Ranaut, 29, already a two-time National award-winner, recently won the best actress honour for her dual role in "Tanu Weds Manu Returns".
"I have asked her for a party. I always say that Kangana is one of the big success stories of Bollywood, from zero to hero. I am very happy for her win," Mehta told PTI.
His last directorial outing, "Aligarh", has won widespread praise for handling the issue of homosexuality in a sensitive manner by re-telling the tragic but true story of Aligarh Muslim University Professor S R Siras.
"Aligarh" starred Manoj Bajpayee and Rajkummar Rao in lead roles. Mehta is already a National awardee as he won the best directing honour for "Shahid" (2013).
