"I have decided to end the agitation. Our demand was that CBI should probe. I have full faith in CBI probe," Sreejith told reporters after ending his sit-in in front of the Secretarait.
The CBI unit here has begun investigations into the case relating to the custodial death of Sreejeev who had died in May 2014, police said.
He was taken into custody on the allegation of a mobile phone theft.
The sit-in had received huge response in social media recently.
Kerala Chief Minister Pinarayi Vijayan had also met Sreejith, promising support.
The LDF government had also written to the CBI asking it to re-examine its earlier decision not to take up the case.