The incident occurred when Gadkari arrived for the rally held in support of BJP candidate Medha Kulkarni. Kothrud police said the person detained appeared to be in an inebriated state and was being questioned.
He is yet to be identified, police said. A BJP spokesman said that the youth was held back by party workers and police immediately, after he tried to get near to Gadkari who was heading towards the podium.
PM and BJP member Narendra Modi and his team have ventured out for marathon election campaigns in Haryana and Maharashtra, which are due on October 15. The results are likely to come out on October 19.