Jason Alexander, 40, accepted the charges. A judge sentenced him to 64 days – the time he has already served.
He was tackled by security after gate-crashing the wedding between Ms Spears and her long-time partner, Sam Asghari.
Alexander was married to the pop star, a childhood friend, in 2004. But the union was annulled after 55 hours.
Spears, 40, and Asghari, 28, tied the knot in a private ceremony at the singer’s home in Ventura County on 9 June.
But preparations were disrupted by Mr Alexander’s arrival. Shortly beforehand he had posted an Instagram Live story in which he said he was there to “crash” the wedding.
His video showed him walking through Spears’ home looking for her, and then going into a marquee where the finishing touches were being put to a large display of roses.
He claimed Spears had invited him, saying: “She’s my first wife, my only wife.” Alexander was arrested and taken to a local jail.
“He was able to find his way onto the property and was confronted by security,” a police spokesman said at the time.
“An altercation occurred with the security officers and that’s where the battery occurred… and during the altercation an item was broken, so that’s where the vandalism comes into play.”
The ceremony went ahead despite the disturbance, attended by stars including Madonna, Paris Hilton,Selena Gomez, Drew Barrymore, Ansel Elgort and will.i.am.
In November, the singer was released from a controversial 13-year legal guardianship, under which her father Jamie controlled many aspects of her life.
Her father, mother and sister were reportedly not at the wedding after relations broke down over the arrangement, and Spears’ legal battle to end it.
Spears met her new husband, a personal trainer, in 2016 on the set of her music video for the song Slumber Party. She was previously married to dancer Kevin Federline from 2004 to 2007.