The serious assault happened at 6pm on Monday in Nimmo Street.
Greenock CID are investigating the incident.
The victim suffered wounds to his head and body and he was rushed to Inverclyde Royal Hospital after the attack.
The man, aged 34, was released after treatment.
Detectives say they are following a positive line of inquiry, but today appealed for witnesses to contact them on 101.Information can also be passed anonymously to Crimestoppers on 0800 555 111.
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