He walked into the showbiz as assistant director to filmmaker Aditya Chopra in Shah Rukh Khan and Kajol's romantic saga Dilwale Dulhania Le Jaayenge, in which he also had a small role.
The son of the late film producer Yash Johar, Karan has doled out entertainers like Kabhi Alvida Naa Kehna, Kabhi Khushi Kabhie Gham and My Name Is Khan, which hinged upon family values and relationships.
As a film producer, Karan has also backed smaller projects like Gippi and Ungli to inject new life into independent cinema.
He wooed the masses with his sharp one-liners and showed off his dance moves as a judge on reality shows like Jhalak Dikhhla Jaa and "India's Got Talent. KJo's tryst with small screen is incomplete without the mention of popular Koffee with Karan series too.
His upcoming projects include Baahubali - The Beginning, Shuddhi and Kapoor and Sons.Here's what the stars tweeted for the multi-talented filmmaker, who has tried his hand at fashion designing too:
To a big brother, a friend and all round great guy. Happy birthday @karanjohar never change!! Biggest hug.
— Abhishek Bachchan (@juniorbachchan) May 25, 2015Happy birthday @karanjohar thank you for being the way you are,love you for it,big hug
— Sidharth Malhotra (@S1dharthM) May 25, 2015Happy birthday @karanjohar ! Wish you never ending happiness, success & hit movies for life!
— ShraddhaVINNIEKapoor (@ShraddhaKapoor) May 25, 2015Happy birthday to my favourite @karanjohar !!!!! Love you love you to the stars and back
— Alia Bhatt (@aliaa08) May 25, 2015#HappyBirthdayKaranJohar @karanjohar hope you have the most amazing year big hug. Wanna dedicate this song to U http://t.co/HYJEbmiyvs
— Varun SURESH Dhawan (@Varun_dvn) May 25, 2015Have a wonderful year @karanjohar love love love
— Dia Mirza (@deespeak) May 25, 2015Happy Birthday my darling @karanjohar Thanks4 being so mad,so talented,so emotional,so wicked & so original always. Love u loads ting
— Preity zinta (@realpreityzinta) May 25, 2015Happy happy @karanjohar here's to flying planes and all the very few things you've left for others to attempt ! Have a swell one !!
— Nimrat Kaur (@NimratOfficial) May 25, 2015Hey K! @karanjohar here's wishing you a very happy birthday, have a blast! Love.
— Aftab Shivdasani (@AftabShivdasani) May 25, 2015Many many happy returns of the day @karanjohar....stay as amazing always!!!!loads of love
— Manish Paul (@ManishPaul03) May 25, 2015Happy birthday @karanjohar! Hope you have a fantastic year :)
— emraan hashmi (@emraanhashmi) May 25, 2015Happy birthday @karanjohar Have a super duper day and a blockbuster year!
— Milap Zaveri (@zmilap) May 25, 2015Happy happy birthday to the guy who has the most wicked sense of humour n enviable wit.The super fun @karanjohar !Love always
— Bipasha Basu (@bipsluvurself) May 25, 2015Happy b'day to the one with the biggest heart, sharpest wit, beautiful mind & toooo much talent! Hv a fab year! Biggest hug@karanjohar
— SOPHIE CHOUDRY (@Sophie_Choudry) May 25, 2015Happy happy happy birthday @karanjohar .... Big love !
— Neha Dhupia (@NehaDhupia) May 25, 2015Happy Birthday Karan. To always growing but never growing old! @karanjohar
— Tanishaa Mukerji (@TanishaaMukerji) May 25, 2015Happy birthday MojoMan!!! I wish you love ishq and a little Mohabbat!!!! I love you! @karanjohar
— Shanoo Sharma (@Shanoozeing) May 25, 2015Happy Birthday @karanjohar
Hope the party and fun you're having in London continues all year. Have a stellar year
— Punit Malhotra (@punitdmalhotra) May 25, 2015Although I wished you personally last night, who doesn't love public attention. Wish you a very Happy Birthday @karanjohar! Lots of love
— Shirish Kunder (@ShirishKunder) May 25, 2015Happy happy bday to a funtastic yaar @karanjohar stay the wonderful person that you are...Lots of love.
— Jackky Bhagnani (@jackkybhagnani) May 25, 2015