A white man attacked the LBC radio presenter while he was standing alone outside the Soho Theatre in central London last night.
Nawaz tweeted a photo of a cut to his forehead and said he was racially abused and then hit in the face with “maybe a signet ring”.
The Met Police said it was called to a report of a racially aggravated assault at 7.10pm.
A spokesperson said the suspect had fled the scene in Dean Street before officers arrived, the BBC reported.
No arrests have been made and an investigation has been launched, the force added.
Nawaz, who presents a show on LBC at weekends, said his attacker took nothing and “ran away like a coward”.
He tweeted: “My forehead will probably be scarred for life. But we will find you, you racist coward, and you will face British justice.”
He said there were witnesses “who heard the racial abuse and have given statements” and added that the police had his attacker’s “face on CCTV”.
Nawaz is the founder of the Quilliam Foundation, a counter-extremism organisation.