"I thank you very much for the kind message of greetings on my birthday. It was thoughtful of you to have remembered my birthday and conveyed your greetings on twitter," she said in a letter to Modi.
Earlier in the day, The Prime Minister tweeted: "Birthday greetings to Jayalalithaa ji. May she be blessed with a long life, filled with good health."
Jayalalithaa, who turned 67 today, also thanked state Govenror K Rosaiah for his greetings.
"I thank you for the kind message of greetings and flowers sent by you on the occasion of my birthday," she said in a message to him.