After his expulsion from the AIADMK, Radhakrishnan accepted an invitation to join the Dravida Munnetra Kazhagam in 2009.

Even though there was an anti-incumbency wave against the DMK, he won the 2011 Assembly election in Tiruchendur constituency.

[5] On 14 May 2015, Radhakrishnan was suspended by the DMK after he and A. Soundara Pandian greeted AIADMK leader Jayalalithaa after she was acquitted in the disproportionate asset case against her.

[6] In the elections of 2016, Radhakrishnan won again in Tiruchendur, beating Sarath Kumar of the AISMK.

In the 2021 assembly election, he again won from Tiruchendur constituency and he was appointed Minister for Fisheries – Fishermen Welfare and Animal Husbandry.