Tagawa had been released on $1,000 bail after being arrested at his Diamond Head home.
Family Court Judge Darryl Choy granted a deferred acceptance of the guilty plea, meaning it will be wiped from Tagawa's criminal record if he stays out of trouble for a year.
Tagawa was placed on probation for one year and fined $1,000. He must also write a letter of apology to the woman.
Defense attorney David Hayakawa said the $1,000 will be contributed to Ala Kuola, a group that helps victims of domestic abuse file temporary restraining orders with Family Court.
The judge scolded Tagawa for missing five court appearances. Choy was upset that an arrest warrant hadn't been issued against the actor.
"There is so much slack here that you could wrap a rope around the world," Choy said.
Following the hearing, Hayakawa said Tagawa would make no comment.
Tagawa, "from the very beginning, took full responsibility for this case. He made no excuses and it took a little while because of his scheduling to wrap this up," Hayakawa said.