The victims, two men in their 70s and 30s, are being treated in hospital with cuts. Both are reported to be in stable condition.
The suspected perpetrator, a 45-year-old man, was reportedly seen running with a knife in the Golders Green area on Wednesday. He was detained by a local security team and has been arrested by police on suspicion of attempted murder in connection with an anti-Semitic attack.
After the arrest, police said the incident was being investigated as a "terrorist act."
London Mayor Sadiq Khan also condemned the attack.
The stabbing follows a series of arson attacks against synagogues and communities in recent weeks.
