Xander was born in Sunnydale, California. His father, Tony, is a hopeless drunk while his mother, Jessica, is a fragile housewife without many maternal instincts. Xander met his life long friend Willow Rosenberg in kindergarten, they briefly dated, but broke up because Xander stole Willow's Barbie doll. Every Christmas Eve, Xander sleeps outside in a sleeping bag, so he won't have to hear his the drunken arguments of his parents. He has a lifelong fear of clowns, resulting from an incident that occurred at his sixth birthday party, in which he was chased by a clown that was hired to entertain the children.
Sunnydale High/Scooby Gang
In the first season of the show, Xander meets Buffy Summers. He overhears Buffy having a strange conversation about demons and vampires with the Sunnydale High School's librarian, Rupert Giles. Xander and Willow soon discover that Sunnydale is situated on top of a Hellmouth. Shortly thereafter, Xander's close friend Jesse is turned into a vampire. Jesse attacks Xander, who is forced to stake him. After these events, he and Willow become side-kicks to Buffy, the vampire slayer, and Giles. As consequence of this he learns everything about the Slayer, as well as the demons and vampires she must fight . He soon begins developing a crush on Buffy, but the feeling isn't returned, though they do become much closer when he saves her life using CPR.
Hellmouth R' US
Xander as well as most of Sunnydale is magically turned into whatever they dressed as for Halloween. Xander was dressed as a soldier. After the spell is broken he retains all the knowledge and skill that a soldier knows. This fact is critical in many episodes as Xander was important in defeating the Mayor.
Willow or Cordelia
With the help of Amy Madison,
he asked her to cast a spell that would make Cordelia fall in love with him, using a necklace as the focal point. But due to unknown circumstances, Amy as well as every other woman in Sunnydale is effected, and Cordelia is not. Every girl in Sunnydale now wants to kill Cordelia because she hates Xander. Cordelia is attacked in the school, but is rescued by Xander. After everything returned to normal, she began dating Xander, much to her friends disliking. But while dating Cordelia, Xander begins to have feelings for Willow again as they kiss or play footsies. But this turns tragically wrong when they cause the accident that brought Cordelia to the brink of death. Not being able to forgive him for having a relationship with Willow while dating her, she breaks up with him. After these events, Cordelia returns to her ways of making fun of Xander and his friends.
Because he is surrounded by a slayer, powerful witch, werewolf, and vampire. He sets out to become to become "tough". During this process he looses his virginity to Faith.
The Road/Back to Sunnydale
After graduating and defeating the Mayor, Xander goes on a cross-country trip. Though he doesn't get far as his car breaks down. He then moves into his parents basement and pays them rent. He soon falls in love with Anya.
"Seven years, [...] Working with the Slayer. Seeing my friends get more and more powerful. [...] All of them. And I'm the guy who fixes the windows."
Xander begins having serious doubts about his relationship with Anya. This fact isn't helped by a summoned demon who makes people sing their feelings. While at their wedding, a demon posing as his future self makes him believe that he and Anya will be trapped in a hate filled marriage like his parents. This false prediction is enough to make him leave her at the alter.
In the last season of the show, Xander and Anya seemed to have become friends again. Though still not as close as when they first dated. Xander's eye is violently taken out by Caleb. In the final battle Anya is killed as Xander calls out for her. Her body is last seen in the ruins of Sunnydale, being swallowed by the Hellmouth.
Post-Sunnydale, Xander is acting as a field operative for the new Watcher's Council, directly under Buffy. He is now, according to the oldest Slayer, a cradle-robbing, dirty pedophile for dating Dawn.