The Congress leader was held after he tried to paste his posters on the banners of BJP's prime ministerial candidate.
Earlier, the city police had detained Mistry and other party workers when they tried to cover BJP banners at advertisement kiosks in Dandiya Bazaar area.
"Mistry and other Congress workers have been detained after they tried to paste his posters on an advertisement kiosk installed on electricity poll on road dividers," Vadodara DCP Dipankar Trivedi said.
Narendra Rawat, the earlier Congress candidate from Vadodara whose candidature was withdrawn after BJP declared that their prime ministerial nominee Narendra Modi will fight from this Lok Sabha seat, and leader of opposition in Vadodara Municipal Corporation (VMC)'s Chandrakant Kastur were also detained along with Mistry and other party workers.
"Mistry or any other Congress leader has not taken any permission for the programme," said Trivedi, adding that further course of action will be decided after looking into the videography of the incident.
"Mistry tried to climb on one pole of road divider for pasting his poster over Narendra Modi's poster, but he was prevented by the police," a Congress worker said.
"Police also took away his ladder which was used to replace Modi's poster," he said further.
Congress workers shouted slogans against Modi and BJP party and alleged that he (Modi) was responsible for not allowing their party candidate to put up his posters.
Talking to PTI, Mistry alleged that police and district administration were acting in a partisan manner and prevented putting up of his posters at advertisements kiosks on city roads.
Mistry also said that when a policeman came to him, he demanded his identity card but the cop refused to show it.
Earlier, Mistry along with other Congress workers sat on a dharna at city Congress office in Dandiya Bazar area of Vadodara city.
Women workers of the party also alleged that they were beaten up by police and in the scuffle their "mangalsutras" were looted and their bangles were broken when they were being detained.
(With inputs from PTI)