Sydney Bristow
Played by Jennifer Garner
Jack Bristow - Sydney's father
Played by Victor Garber
Michael Vaughn - Sydney's love interest and former CIA handler
Played by Michael Vartan
Eric Weiss - Vaughn's best friend, and possibly the new boyfriend of Nadia (he also works with the rest of the gang)
Played by Greg Grunberg
Marcus Dixon (on the left) - Sydney's friend and former SD-6 partner
Played by Carl Lumbly
Marshall Flinkman - The APO gang's tech and gadgets man
Played by Kevin Weisman
Arvin Sloane - The former head of SD-6 and currently Sydney's superior, father of Sydney's half sister Nadia Santos
Played by Ron Rifkin
Nadia Santos - Sydney's half sister, daughter of Sloane
Played by Mia Maestro
Julian Sark - Enemy
Played by David Anders
Irina Derevko - Sydney's mother, formerly Laura Bristow, former KGB spy, mother of Nadia Santos
Played by Lena Olin
Lauren Reed - Vaughn's deceased wife, traitor, member of the terrorist organization known as the Covenant
Played by Melissa George
Daniel (Danny) Hecht - Sydney's fiance murdered upon the orders of Arvin Sloane, the then head of SD-6