Anil has done a voice over for the character of Karna while Manoj has dubbed for Yudhishtir's character in the animated retelling of the Indian epic.
Film's producer Jayantilal Gada confirmed their addition to the cast.
"Both Anil and Manoj have shown full commitment. It was very gracious on their part to agree to impart voices to two very important characters in my film," he said.
Anil took 15 days to complete his work, while Manoj worked on the project for four days.
The animation film has a star-studded cast of voices of Amitabh Bachchan (Bheeshma Pitamah), Vidya Balan (Draupadi), Sunny Deol (Bheem) and Ajay Devgn (Arjun).
Gada is planning to release the film this Diwali.
When asked about a clash with other big festival release 'Krrish 3', he said, "No, we are not going to clash with Hrithik Roshan's film, we will release a week before or later, but in the festive season.