The 42-year-old director-producer, who joined twitter in July, 2009, thanked his fans for helping him achieve this feat.
At 6 million today on Twitter... Thank you for the love... The hate... The indifference and most of all the acknowledgement," Johar tweeted.
The filmmaker is gearing up for the release of Anurag Kashyap's "Bombay Velvet", in which he has a full-fledged role opposite Ranbir Kapoor and Anushka Sharma.
Johar had earlier done bit roles in films like "Dilwale Dulhaniya Le Jayenge", "Salaam -e-Ishq", "Luck By Chance" among others.