Rajendra Nath was a comedian actor in Indian Hindi films. Rajendra Nath's brother Prem Nath went to Mumbai and became an actor, so Rajendra Nath joined him, they were good friends of Raj Kapoor and Shammi Kapoor. Rajendera Nath and Prem Nath's sister Krishna is married to Raj Kapoor.
Initially Rajendra Nath struggled to get roles till Sashadhar Mukherjee offered him a comedian's role in Dil Deke Dekho, a film directed by Nasir Hussain, starring Shammi Kapoor and Asha Parekh. In Nasir Hussain's Jab Pyar Kisi Se Hota Hai he along with Asha Parekh were a regular in many Nasir Hussain films- like Phir Wohi Dil Laya Hoon, Teesri Manzil, Baharon Ke Sapne, Pyar Ka Mausam. He once played a buffoon called Popatlal in Jab Pyar Kisi Se Hota Hai, and the name grew synonymous with Rajendra Nath.