Ned Arnel Holness was born in San Pedro Sula, Honduras, the seventeenth of eighteen children. At the time of his birth, his mother, Magdelena Menc?a from Mexico, was engaged in a domestic dispute with his father, Honduran Roberto Holness, and declined to give her son his biological father's last name. The name appearing on his birth certificate is "Ned Arnel Menc?a", although Mencia has said that out of respect for his biological father he went by the Holness name anyway, and was known as "Ned Holness" until he was eighteen years old.
Mencia was raised in East Los Angeles, California by his aunt Consuelo and uncle Pablo Mencia. By his own admission, staying out of trouble was difficult while growing up, but with the help of his family he excelled in school and stayed out of gangs. He majored in electrical engineering at California State University, Los Angeles, but left early to pursue a career in comedy after a successful performance at an open mic night at The Laugh Factory. He also has an older brother named Joseph Mencia who often appears on Carlos' program Mind of Mencia.
Mencia currently lives with his wife, Amy, in the Los Angeles area in California.They have one child, Lucas Pablo Mencia.