The duo took to social media penned the emotional posts.
"1 year of 'Dhadak'. 1 year of Madhu and Parthavi. 1 year of this family, of your love, of all these memories and people that I will cherish my whole life and never let go of," wrote Janhvi.
Directed by Shashank Khaitan, "Dhadak" is a remake of Marathi film "Sairat". It is produced by Karan Johar.
Janhvi thanked Karan, her "guiding light", for giving her the opportunity that set her "on a path I've always only dreamed of."
She praised Shashank and Ishaan too.
"Shashank, every step of this journey I looked up to you more and more. Thank you for everything you've taught me, for being there for me and for giving us more love than we could have ever hoped for.
"Ishaan, Mr. Madhukar Bagla, Nothing I say will be enough to sum up how happy I am that we went on this journey together and had each other to lean on, to argue with, and to find comfort in," wrote Janhvi.
Ishaan, who made his acting debut with Majid Majidi's international project "Beyond the Clouds" before "Dhadak", reminisced his time on the sets of the Shashank Khaitan film.
"Major nostalgia ensues and will continue for the next few hours. Thank you to Karan, Shashank, Janhvi, who have etched themselves into my life and my most prized memories forever... and to the entire cast and crew without whom our film's heart would not beat as it did," wrote Ishaan.
( With inputs from IANS )