Estevez was born in The Bronx,[1] the oldest child of artist Janet Sheen and actor Martin Sheen (legally Ramón Estévez). His siblings are Ramon Estevez, Charlie Sheen (born Carlos Estévez), and Renée Estevez. Estevez's paternal grandparents were Irish and Galician immigrants. His father is a "devout Catholic" and his mother is a "strict Southern Baptist."[2]

Estevez initially attended school in the New York City public school system but transferred to a private academy once his father's career took off. He lived on Manhattan's Upper West Side until his family moved west in 1968 when his father was cast in Catch-22. Growing up in Malibu, California, Estevez attended Santa Monica High School.

When Estevez was 11 years old, his father bought the family a portable movie camera.[3] Estevez also appeared in Meet Mr. Bomb, a short anti-nuclear power film produced at his high school.[4] Estevez was 14 when he accompanied his father to the Philippines, where Sheen was shooting Apocalypse Now.[3] Estevez had a role as an extra in Apocalypse Now, but his scenes were deleted.[5]

When they returned to Los Angeles, Estevez co-wrote and starred in a high school play about Vietnam veterans called Echoes of an Era and invited his parents to watch it. Sheen recalls being astonished by his son's performance, and "began to realize: my God, he's one of us."[6] After graduating from Santa Monica High in 1980, he refused to go to college and instead went into acting.[3] Unlike his brother Charlie, Estevez and his other siblings did not adopt their father's stage name. Emilio reportedly liked the alliteration of the double 'E' initials,[7] and "didn't want to ride into the business as 'Martin Sheen's son'."[3] Upon his brother's using his birth name Carlos Estevez for the film Machete Kills, Estevez mentioned that he was proud of his Spanish heritage and was glad that he never adopted a stage name, taking advice from his father who regretted adopting the name Martin Sheen as opposed to using his birth name, Ramón Estévez.