Officers were called to Willesden High Road, NW10, at around 11.45am on Monday, July 7, after reports of an altercation.
A man in his 30s was found with facial injuries after being slashed with a knife.
He was treated at the scene by paramedics before being taken to hospital.
His injuries were later confirmed as not life-threatening or life-changing.
Police believe the attack was unprovoked.
No arrests have been made.
The man officers are trying to identify is described as lack, around six foot tall, of medium build, bald, and with a goatee.
He was wearing a white hoodie with black print on the arms and red tracksuit bottoms when caught on CCTV.
He is also believed to have returned to the scene on Friday, August 29, to ask about the incident.
On that occasion, CCTV shows him in a navy t-shirt with “Lost in the Waves” across the front and light blue jeans.
Detective Constable Gabriela Cociasi, leading the investigation, said: “This attack happened in the middle of the morning on a busy high street.
“Its brazen nature will understandably alarm the community, however our officers continue to work tirelessly to identify the suspect. We now need your help.
“If anyone knows who this man is, or has any information in relation to the incident on Monday, 7 July, please contact us as a matter of urgency on 101 quoting CAD 3149/07JUL25.
“If you see him in the community, do not approach him and instead dial 999.”
“Those who want to share information and remain anonymous can contact Crimestoppers on 0800 555 111.”
