The Indian Express reported that Patel joined the party during the Congress Working Committee (CWC) meet in Gujarat.
Justifying his decision to enter active politics ahead of the Lok Sabha polls, Patel said he could now work for the six crore people of Gujarat in a better way.
Targeting Prime Minister Narendra Modi, Patel said when the Congress decided to postpone its rally, earlier scheduled for 28 February, following the terror attack in Pulwama last month, the Prime Minister was busy addressing gatherings across the country.
The 25-year-old Patidar leader praised Rahul Gandhi, saying the Congress president is “honest”.
“People ask me why I chose the Congress and Rahul Gandhi. I chose Rahul Gandhi because he is honest. He does not believe in working like a dictator,” he said.
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.
In July last year, the sessions court of Visnagar in Mehsana district had sentenced him to two years imprisonment for rioting and arson which took place in Visnagar town in 2015.
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.
(With PTI inputs)