In an Instagram livestream, Alexander was shown approaching Spears’s home in Thousand Oaks, California, and entering before being stopped by security officers.
“Don’t put your hands on me,” he is heard saying at the beginning of the video. “Please don’t put your hands on me.”
He continued live streaming and exited the home, approaching an event tent.
“Hey, where’s Britney at?” he asked a bystander. “I’m Jason Alexander, her first husband, I’m here to crash the wedding, brother.”
He was later accosted by officers and arrested for an out-of-county warrant, the Ventura Country Sheriff’s department confirmed to The Hill. Police are still investigating the scene.
Alexander and Spears married in 2004 in Las Vegas. The pair, who were childhood sweethearts, had the union annulled only 55 hours later.
Spears was set to marry Asghari, a 28-year-old personal trainer, on Thursday. It will be her third marriage.