Sanjeev Jha, who is the MLA from Burari constituency in north Delhi, was detained along with the party supporters Aashish Tyagi and Neeraj Pathak around 12.20 p.m.
Police said that the legislator and his associates were detained for a few minutes for breach of code of conduct as they were wandering near Ramjas College while voting was going on.
AAP volunteer Aashish Tyagi also confirmed the detention.
"I along with Sanjeev Jha and Neeraj Pathak were walking on the footpath near Ramjas College when a police team approached us and took to a nearby police outpost," Tyagi told IANS.
"We were kept under detention for around 10 minutes and then allowed to go, with a warning not to visit any DU colleges while voting takes place," he said.