The Gay Men's Chorus of Los Angeles provided entertainment before the swearing in.
Perez, 40, is a cousin of Los Angeles Mayor Antonio Villaraigosa and was able to win the speaker's post ahead of more experienced members of the Democratic party.
Even before the swearing-in, Perez guided the vote against confirming Gov. Arnold Schwarzenegger's pick for lieutenant governor, state Sen. Abel Maldonado.
The governor has resubmitted Maldonado's nomination and the vote will come up again.
Perez replaces Karen Bass, who will be termed out at the end of the year in her 47th Assembly District seat. She is currently running for the 33rd Congressional District seat.
Perez is taking leadership of the 80-member house as the state is dealing with a $20-billion budget deficit and statewide unemployment is at 12 percent.
Perez becomes the 68th Assembly speaker and can serve four more years in the Assembly.