Born on 10 December 1978, Summer Joy Phoenix is the fifth and youngest child of Arlyn and John Phoenix, a carpenter. Summer was raised in Southern California, but spent her teen years in Central Florida, where she was born. She is an active supporter of numerous charities and activist groups, mainly concerning the environment, animal rights and vegetarianism. Summer has also appeared in many print ads in Europe.

Summer is married to actor Casey Affleck.
Born at 2:34 AM EST Competed with her sister, Liberty Phoenix, for the part of "Candi" in Russkies Sister of River Phoenix, Joaquin Phoenix, Rain Phoenix and Liberty Phoenix. Is a vegan. Attended New York University's Tisch School of the Arts film school. [January 1997 - May 1998] Was a member of the (now defunct) quasi-religious alternative band "The Causey Way" (along with her elder sister Rain Phoenix). She played keyboards and sang back vocals, occasionally. In keeping with the pseudo-religious "Causey" theme, each band member, when they were inducted, was given a new Causey name. Summer's Causey name was "Sum Sum Causey". April/May 2002: Appeared at London's Garrick Theatre, in "This Is Our Youth", alongside Matt Damon and Casey Affleck. Her name, Summer Joy, represented her families reaction to being back in the United States after leaving the religious cult, The Children of God. Wrote/Played some piano pieces on her sister Rain Phoenix's new CD. Often works with good friend Clea DuVall. Became engaged to boyfriend actor Casey Affleck over Christmas 2003. Her brother, the late River Phoenix, played the young Harrison Ford in Indiana Jones and the Last Crusade. Her soon-to-be brother-in-law, Ben Affleck, played the younger version of Harrison Ford's character in The Sum of All Fears. Gave birth to son, Indiana August, May 31, 2004 in Amsterdam Named her son Indiana. Her late brother, River Phoenix, played young Indiana Jones in Indiana Jones and the Last Crusade. Is a member of "The Paper Cranes", an alternative band that plays the New York City club scene. She plays the Rhodes, piano and guitar. They have released an EP and have plans to produce more. Her sister, Rain Phoenix, is the band's lead vocalist. "Paper Cranes" plays mostly shows in Gainesville, Florida. Opened a recycled vintage clothing boutique on Manhattan's Lower East Side called "Some Odd Rubies" which she co-owns with Odessa Whitmire (Matt Damon's ex-girlfriend) and Ruby Canner (a childhood friend). [May 2003] Appears in Girl with Sean Patrick Flanery, who, like her brother River Phoenix, played the young Indiana Jones. Sister-in-law of Ben Affleck and Jennifer Garner.