Doherty's dad suffered a near-fatal stroke last Christmas which impaired his ability to communicate.
"When I mentioned [Dancing With The Stars] to him, he got really excited, and he wanted me to do it," Doherty told People. "I thought, if my dad can fight through having a stroke and the loss of being able to communicate, I think I can do this for him. So I figured I'm going to get over my fear for him."
The actress suffers from stage fright and had previously turned down chances to compete on the reality show.
"I have a huge fear of live audiences," she said. "I break out in hives, full blown panic attacks, and everything else."
Doherty added that she expects to have a good time on the show after positive reports from former 90210 co-stars and Dancing competitors Ian Ziering and Jennie Garth.
"Everyone who I know who's been on the show has had a great time," Doherty affirmed. "It's with hesitation and fear, but it's going to be good to conquer a fear."
The tenth season of Dancing With The Stars premieres on the ABC network on March 22.