"The Prime Minister should take pity on Mr Tharoor, find out whether he needs medical help, and send him to a mental hospital if needed," he told ANI.
Swamy's suggestion came a day after Tharoor's said India would become a 'Hindu Pakistan' if BJP is re-elected in 2019.
"I don't know if he overdosed on something. His comments clearly exhibit frustration. What is the definition of Hindu Pakistan? What does he mean? Is he against Pakistan? He appeases Pakistanis so much and asks Pakistan Prime Minister to help remove Prime Minister Modi from power. He has also got Pakistani girlfriends. They are ISI people," he added.
The senior BJP leader further sought the Congress' stance on Tharoor's remark.
"They (Congress) spoke about Hindu terror earlier, but that turned out to be a fiasco. The Congress leadership should disown it (Tharoor's comments), otherwise it'll mean they are in a state of frustration," he explained.
Addressing an event in Thiruvananthapuram, Tharoor, on Wednesday, stated that the BJP will write a new Constitution, which will pave the way for a nation, much like Pakistan, where rights of minorities are not respected.
He said that if re-elected, the BJP will "tear apart" the constitution and will write a new one "which will enshrine principles of Hindu Rashtra, that will remove equality for minorities and create a Hindu Pakistan."