Susi, who played the voice of Howard's (Simon Helberg) mother Mrs Wolowitz, died last week due to cancer, reported E!Online.
Nayyar, 33, who plays Raj on the hit CBS sitcom, appeared on 'The Ellen DeGeneres Show'to talk about losing Susi and gave a sincerely heartfelt tribute to his late co-star.
"Sadly, a couple of days ago, we lost one of our cast members. She's famous because of her voice. She unfortunately lost her battle with cancer. We will miss her and she was a lovely lady. Her spirit will live with us on set forever," he said.
"She's the only person I know in Los Angeles who didn't drive. For 30 years, she didn't drive a car. She would take the bus to work at Big Bang!," he added.