"Heartiest congratulations to Shri #RamNathKovind ji on his nomination as our candidate for the office of President of India," she tweeted.
On Saturday, Swaraj had dismissed reports that she was a contender in the presidential poll as "rumours".
Ram Nath Kovind, the governor of Bihar, is the NDA's candidate for the 13th President of India. His name was announced by BJP chief Amit Shah today after a meeting of the parliamentary party - the BJP's highest decision-making body.
Mr Kovind will file nomination for President's position on June 23, Mr Shah said. If elected, he will be the second Dalit President after KR Narayanan to hold the nation's highest office.