Senior AAP leader Sanjay Singh attributed the merger to a "rising tide of support" for AAP as the poll campaigning enters the last leg.
Khan led around 300 workers and top office bearers of the Peace Party including its state general secretary Nazakat Ali, Delhi vice president Fakruddin Saifi and UP general secretary Brij Kishore, while joining AAP during a press conference.
"The 49-day government of AAP provided transparent governance like never before. We are joining the party at the last moment to give it the final push ahead of the polls," Khan said.
Peace Party candidates, who had contested the 2013 Delhi Assembly elections, also pledged their support to the AAP candidates, particularly in east and northeast Delhi.
Yesterday, Congress leader Sanjey Puri had joined AAP along with Delhi Mahila Congress secretary Neena Kapoor.
Few other leaders also joined AAP including sitting independent MCD councillor Poonam Bhardwaj, BSP leader Narender Jat Rana and Surinder Bhardwaj of SP. Both of them contested the 2013 Assembly elections from the Bijwasan Assembly constituency.