Speaking to IANS, the official said Rajeesh Kumar, 24, will be presented before a magistrate.
"He has been arrested for defaming the prime minister through his objectionable posts," added the official.
The police registered a case after Umesh Babu, an office-bearer of the Kollam unit of the Rashtriya Swayamsevak Sangh, complained that Kumar has been using the social media to defame Modi.
Police picked up Kumar Monday and interrogated him. After checking with the Cyber Police if he had committed a crime, the police arrested him Tuesday.