Johar attended a screening of the movie, which he found "poignant, moving and heartbreaking".
"'Aligarh' is exceptionally poignant, moving and heartbreaking in equal measure....a relevant and important film of our times," Karan tweeted on Wednesday.
The film is based on the real-life of Shrinivas Ramchandra Siras, a professor at Aligarh Muslim University who was removed from his job for homosexuality.
Actor Manoj Bajpayee essays a professor, while actor Rajkummar Rao plays a journalist in the film.
Praising their work, Karan shared: "@mehtahansal and @Apurvasrani tell a strong narrative with genius subtlety and command...@BajpayeeManoj and @RajkummarRao are exceptional".
"Aligarh" will release on February 26.