Trini Mitchum is the youngest child of actor Robert Mitchum and Dorothy Spence Mitchum. Her full name is Petrine Day Mitchum. She is a filmmaker, author, photojournalist and former Hollywood story editor.She is best known for Hollywood Hoofbeats, a book about horses in movies and television.
She also made short films that aired on Saturday Night Live and helped bring a documentary about her father to Turner Classic Movies.This guide pulls together verified facts, clears up name and birth year confusion, and shows what her career looks like in 2026.
Trini Mitchum Quick Facts
| Detail | Verified Information |
| Full name | Petrine Day Mitchum |
| Also credited as | Trini Mitchum, Trina Mitchum |
| Birth date | March 3, 1952, per her mother’s obituary (IMDb lists 1954) |
| Birthplace | Los Angeles, California |
| Age in 2026 | 74 if the 1952 date is correct |
| Father | Robert Mitchum (1917 to 1997) |
| Mother | Dorothy Spence Mitchum (1919 to 2014) |
| Siblings | James “Jim” Mitchum (died September 20, 2025) and Christopher Mitchum |
| Main profession | Filmmaker, author, photojournalist, film historian |
| Acting credit | Billed as “3rd Hippie” in The Mechanic (1972) |
| Industry jobs | Story editor and script analyst for The Ladd Company, Pathé, TriStar Pictures and DreamWorks |
| Short films | Under the Thinking Cap and Out of Gas (both linked to Saturday Night Live) |
| Out of Gas details | Aired on the November 14, 1987 episode hosted by Robert Mitchum; licensed by TCM in 2018 |
| Best-known book | Hollywood Hoofbeats with Audrey Pavia (first edition 2005, second edition 2014) |
| Other books | Snout About Town Starring Buster Keaton Browne; co-wrote Nudie Cohn’s memoir (1978) |
| Documentary work | Co-producer credit on James Stewart, Robert Mitchum: The Two Faces of America; director of From Rawhide to Rhinestones: How the West Is Worn |
| Home base | Santa Ynez Valley, California (since 2006) |
| Net worth | No verified figure exists |
Growing Up in the Mitchum Family
Trini Mitchum was the third and last child of Robert and Dorothy Mitchum. She was born in Los Angeles on March 3, 1952. Her mother’s obituary, published in 2014, describes her as a surprise third child.
Her brothers, James and Christopher, were already growing up in a famous household. Robert Mitchum was one of Hollywood’s best-known leading men. He starred in Out of the Past, The Night of the Hunter and Cape Fear.
Her childhood was not spent only in Hollywood. A Santa Ynez Valley newspaper reported that the family often lived in horse-friendly places. These included a Maryland farm and Mandeville Canyon in Los Angeles, where she learned to ride.
Here is the family timeline in short:
- 1940: Robert and Dorothy marry, according to IMDb.
- 1952: Petrine Day Mitchum is born.
- 1960 to 1966: The family lives on Maryland’s Eastern Shore.
- 1977: Robert and Dorothy move to Montecito, near Santa Barbara.
- July 1, 1997: Robert Mitchum dies at age 79.
- April 12, 2014: Dorothy Mitchum dies at age 94.
Dorothy was a writer and community volunteer. Petrine later wrote a tribute to her mother after her death.
Why She Uses More Than One Name
Many readers get confused because she appears under three names. They all point to the same woman.
- Petrine Day Mitchum: Her full name. It appears on her books, author pages and documentary credits.
- Trini Mitchum: The name used in many family and web profiles.
- Trina Mitchum: The spelling in some film credits and fan write-ups.
IMDb even keeps two separate pages for her, one under Trina and one under Petrine Day. That split makes her credits look smaller than they are.
No reliable source explains how the nickname began. Treat any neat origin story you read online with caution.
Birth Year: 1952 or 1954?
Her mother’s obituary lists March 3, 1952. IMDb and many copycat sites say 1954. The obituary is the stronger source because it was written by family. This article uses 1952 and flags the conflict.
A Small Acting Role Came First
Her only known screen role came in the 1972 crime thriller The Mechanic, starring Charles Bronson. IMDb credits her as “3rd Hippie.”
It was a tiny part. It did not launch an acting career, and she did not chase one. A 1973 quote attributed to her calls her father “a pretty fair man,” which suggests she saw him as a parent first and a movie star second.
Her real path ran behind the camera.
Years of Work Behind the Camera
Before she was a published author, she worked inside the studio system. The Center for Independent Documentary lists her as a former story editor and analyst at four companies:
- The Ladd Company
- Pathé
- TriStar Pictures
- DreamWorks
What a Story Editor Actually Does
A story editor reads scripts, books and pitches. A script analyst writes coverage, which is a short report on whether a project works. Studios use this feedback to decide what to develop.
It is quiet work. Audiences never see it. But it trains a person to understand structure, character and pacing, and that skill shows up in her later films and books.
Her Short Films Reached Saturday Night Live
Two of her short films are tied to Saturday Night Live:
- Under the Thinking Cap, made with artist Pippa Garner
- Out of Gas, starring Robert Mitchum and Jane Greer
The Story Behind Out of Gas
Out of Gas played on the November 14, 1987 episode, when Robert Mitchum hosted the show. It was a spoof of Out of the Past, the 1947 film noir that made both Mitchum and Greer famous.
Fan episode guides describe the setup. Mitchum plays Jeff Bailey at what is called the last leaded gas station in America. Greer returns as Kathie. Her nephew, Bentley Mitchum, plays The Kid.
Turner Classic Movies licensed Out of Gas in 2018. That gave a 1987 short a second life for classic film fans.
Hollywood Hoofbeats Became Her Main Book
Hollywood Hoofbeats: Trails Blazed Across the Silver Screen is the work most linked with Trini Mitchum. She wrote it with Audrey Pavia, an editor and writer who specializes in animal topics.
How the Book Began
The project started in the late 1990s. She was brought in as a consultant on a documentary about Hollywood horses. That film was never finished. She kept the interviews, photos and research from about five years of work and turned them into a book.
The Two Editions
| Edition | Year | Publisher | Notes |
| First | 2005 | BowTie Press | Launch event held at the Autry National Center in Los Angeles on November 10, 2005 |
| Second | 2014 | I-5 Press | Added about two more years of research and new films |
The 2014 update added movies such as War Horse, Secretariat, Django Unchained, Avatar and the remakes of True Grit and The Lone Ranger.
In 2016, she discussed the book on NPR’s Fresh Air with Dave Davies. She talked about silent film star horses, stunt training and how James Stewart bonded with his horse Pie.
A Film History Book With a Clear Purpose
Hollywood Hoofbeats is not a family memoir. It is a history of the animals that helped build the movie business.
Her central argument is simple. Film as we know it grew out of an experiment with a camera and a horse. She points to Eadweard Muybridge’s motion studies in the 1870s. Without horses, she says, there would be no classic Westerns and no Ben-Hur.
The book covers:
- Famous screen horses such as Trigger and Champion
- Trainers, stuntmen and stunt horses
- Funny and clever animal performances
- The cruel trip wire falls of early filmmaking
- How public pressure led to animal safety oversight
On that last point, she credits Errol Flynn’s public criticism after the 1936 film The Charge of the Light Brigade as a turning point. It helped lead to American Humane Association monitoring on film sets.
A reviewer at CowboyWay described the book as a loving encyclopedia of movie horses. That fits its tone. It is detailed, but it reads like a tribute.
Writing, Photos, and Western Culture
Her work reaches beyond one book. She has written as a photojournalist and essayist, including for Horse Illustrated.
Western culture is a steady thread in her career:
- 1978: She co-wrote the memoir of Nudie Cohn, the tailor famous for rhinestone Western suits, according to the Center for Independent Documentary.
- Documentary series: She directs From Rawhide to Rhinestones: How the West Is Worn. It grew out of an earlier project about Nudie Cohn.
- Team: She works with writer and producer Holly George-Warren, and the team has included producer Dub Cornett and costume designer Cathy A. Smith.
- 2025: She was listed on a “Nudie Suit” roundtable at a pop culture convention.
- Children’s book: Snout About Town Starring Buster Keaton Browne promotes dog adoption.
The documentary expanded to trace Western fashion from Native American buckskin to modern runways. IMDb lists it as in pre-production, and no confirmed release date has been published.
Helping Tell Robert Mitchum’s Story
The Center for Independent Documentary credits her as a co-producer of James Stewart, Robert Mitchum: The Two Faces of America. French filmmaker Grégory Monro directed it in 2017.
The film compares two stars who died within a day of each other in 1997. Stewart often played the dependable hero. Mitchum became the cool, dangerous antihero. TCM’s own listing names Monro as director and Céline Loiseau as producer, so her role is best described as co-producer and on-camera family voice.
She also appears in the film as herself, speaking as Robert Mitchum’s daughter. It debuted on Turner Classic Movies in January 2019.
She has also appeared as an interviewee in other Mitchum related material, including a DVD commentary for David Lean’s Ryan’s Daughter, a film her father starred in.
Horses Stayed Part of Her Life
Horses were never just a research topic. She has lived in California’s Santa Ynez Valley since 2006, after decades of visiting.
A 2014 newspaper profile described her life there with two rescue dogs and an American Quarter Horse named Dillon. Her publisher biography later listed two quarter horses, Genuine Rascal Jac and Photo Op.
Animal welfare appears in her local work too. Her book Snout About Town was a tribute to her dog Buster, who died in 2014. She planned signings where a share of sales supported the Santa Ynez Valley Humane Society in Buellton.
James and Christopher Took a Different Road
Her brothers chose acting. Trini Mitchum chose storytelling from behind the scenes.
James “Jim” Mitchum
- Appeared in his first film at age 8
- Played his father’s younger brother in Thunder Road (1958), which Robert produced
- Starred in Moonrunners (1975)
- Appeared in about 35 productions before retiring in 1994
- Later launched a whiskey line honoring his father’s films
- Died September 20, 2025, at age 84 in Skull Valley, Arizona
Christopher Mitchum
Christopher Mitchum built a long acting career and also worked in politics. He was named as a surviving brother in Jim’s October 2025 obituary.
The same obituary listed Petrine Day Mitchum as a surviving sister. That is useful proof she is alive and part of the family record.
Her Life and Work in 2026
As of November 2026, Trini Mitchum is best described as an author, filmmaker and film historian based in the Santa Ynez Valley.
Here is what current public records show:
- From Rawhide to Rhinestones is listed as in development.
- A documentary version of Hollywood Hoofbeats has been mentioned in author biographies.
- Her books remain in library and bookseller catalogs.
- She keeps her private life out of the spotlight.
Claims You Should Not Trust
Many low quality sites repeat errors. Be careful with these:
- “She died in 2000.” False. She was named as a living sister in a 2025 obituary.
- “She starred in The Hardy Boys.” No reliable credit supports this.
- “Her net worth is $100,000.” No credible source verifies any figure.
- “She is a celebrated actress.” Her acting work was one small part in 1972.
Final word
Robert Mitchum will always be part of her name. But Trini Mitchum built something separate from his fame.
Her story shows that growing up near fame does not decide your path. She studied the movies, found a niche and made it her own.
FAQs
Who is Trini Mitchum?
Trini Mitchum is Petrine Day Mitchum, the daughter of Robert and Dorothy Mitchum. She is a filmmaker, author and former story editor.
How old is Trini Mitchum in 2026?
She is 74 if her March 3, 1952 birth date is correct. IMDb lists 1954, which would make her 72.
Is Trini Mitchum Robert Mitchum’s only daughter?
Yes. She was the youngest of his three children and his only daughter.
What is Trini Mitchum best known for?
She is best known for co-writing Hollywood Hoofbeats, a book about horses in film and television.
Did Trini Mitchum appear on Saturday Night Live?
Her short films did. Out of Gas aired on the November 14, 1987 episode hosted by her father.
What movie did Trini Mitchum act in?
She played “3rd Hippie” in the 1972 film The Mechanic.
Who are Trini Mitchum’s brothers?
They are James “Jim” Mitchum, who died in 2025, and Christopher Mitchum.
Where does Trini Mitchum live?
Author biographies place her in California’s Santa Ynez Valley, where she has lived since 2006.
Is Trini Mitchum married?
IMDb lists a 1980 marriage to John S. Richardson, but there is no recent public confirmation.
What is Trini Mitchum working on now?
She is linked to From Rawhide to Rhinestones, a documentary series on Western fashion, which is listed as in pre-production.
