Peter Miguel Camejo's family is from Venezuela, but he was born in New York on December 31, 1939. Camejo attended the Massachusetts Institute of Technology, but left to study history at the University of California in Berkeley. He was suspended from Berkeley for using an unauthorized microphone when protesting against the Vietnam War. In the 1960s, Camejo organized rallies supporting civil rights, and went to Selma, Alabama to march with Reverend Martin Luther King Jr.

Camejo was the Socialist Party candidate for president in 1976. The Socialist Party is a third party that supports public spending on education and worker's rights. In 1985, Camejo became a stockbroker. He later co-founded an investment firm that only supports socially responsible companies. Camejo and his wife, Morella, have two children. They live in Folsom, California. Camejo was the Green Party candidate for governor of California in the 2003 special election. Arnold Schwarzenegger won that election.

Camejo worked for environmental groups that promote conservation through education. He has written about and supports socially responsible investment as both a businessman and a politician.