However, Patel's plans to contest the Lok Sabha polls, the schedule of which was announced by the Election Commission of India on Sunday, may be possible only if he clears legal hurdles.
He has been convicted and sentenced to two years in a riot case connected to the 2015 Patidar quota agitation, which bars him from contesting polls.
"To give shape to my intentions to serve society & country, I have decided to join Indian National Congress on 12th March in presence of Shri Rahul Gandhi & other senior leaders," Patel tweeted Sunday.
"I would also like to state that if there is no legal hindrance and party decides to field me in electoral politics, I would abide by the party's decision. I am taking this step to serve 125 crore citizens of India," he said in another tweet.
While his jail term has been stayed by the court, his conviction has not been suspended.
Patel has filed a petition in the Gujarat High Court seeking a stay on his conviction by a lower court.
Earlier, on Friday, the Patidar Anamat Andolan Samiti (PAAS) had given the go-ahead to Patel to join the Congress.
Patel has earlier indicated that he wanted to contest Lok Sabha polls from Jamnagar seat.
While Congress state unit chief Amit Chavda said Patel's induction into the party would strengthen it, Gujarat Chief Minister Vijay Rupani said the decision proved that the PAAS leader was a "design of the Congress".
"We have been saying this, and now it has been proved that Hardik is a design of Congress party. His agitation was at the behest of the Congress. He has cheated his community, misled youth. He would get a befitting reply from the Patidar community if he stood for polls," Rupani said.
"Till now Hardik was leading a social agitation. Now when he joins the Congress party, it will strengthen us in Gujarat," Chavda said.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)