He and his family were all vegetarians. He believed that eating animals was wrong and was the one who, as a child, convinced his family to become vegans. His opinions on the issue were so strong that when his actress girlfriend, Martha Plimpton, ordered soft-shell crab at a restaurant, he was reported to have begun to cry in disappointment.
Phoenix was one of five siblings who pursued careers in show business, encouraged by their parents, former Children of God missionaries. He had significant juvenile roles in Stand by Me and The Mosquito Coast and portrayed a teenage Indiana Jones. He later went on to star opposite Keanu Reeves in Gus van Sant's My Own Private Idaho. He was friends with both of them and their friendship continued beyond the movie. River was also a friend of John Frusciante (guitarist for the Red Hot Chili Peppers) and appeared on his debut album on the song Soul Removal.
River disliked being seen as just a sex symbol.
So far, of his siblings, his younger brother Joaquin has achieved the greatest success, with his first major role coming in another Gus van Sant movie To Die For, opposite Nicole Kidman. His sister, Rain, appeared in van Sant's adaptation of Tom Robbins's story Even Cowgirls Get the Blues alongside many other well-known personalities.
- Silent Tongue (1994)
- Dark Blood (1993)
- Even Cowgirls Get the Blues (1993)
- Thing Called Love (1993)
- Sneakers (1992)
- Dogfight (1991)
- My Own Private Idaho (1991)
- I Love You to Death (1990)
- Indiana Jones and the Last Crusade (1989)
- Night in the Life of Jimmy Reardon, A
- Running on Empty (1988)
- Little Nikita (1988)
- The Mosquito Coast (1986)
- Circle of Violence: A Family Drama (1986) (TV)
- Stand by Me (1986)
- Explorers (1985)
- Surviving (1985) (TV)