He was joined by Hillingdon councillors in Joel Street boulevard, outside the underground station, where he also unveiled a commemorative plaque, skidded around on new paving stones and fawned over new murals.
Arriving from the station, he declared: “My God, it's beautiful! Did we do this? The murals – they're sensational!”
He added: “I think it's all fantastic, really imaginative. I'm very proud.”
The project has been funded by £1.3million from the mayor's regeneration fund and £450,000 from Hillingdon Council, plus additional cash from Transport for London.
The money has been spent lining the central boulevard with trees, improving the shop fronts of 24 independent businesses and creating 30-minute 'stop and shop' parking bays.
Additionally, the road bridge over the railway is now home to Europe's longest enamel mural, created by graffiti artists Cosmo Sarson and Gordon Collett.
Mr Johnson said: “Northwood Hills is an important local hub supporting a range of shops and services. The improvements that I have seen here today are a great example of how my regeneration fund is helping to spruce up town centres and high streets across London, rejuvenating areas for local communities to enjoy and helping enterprises to thrive.”
Members of the public were keen to meet and take selfies with the mayor as he strolled into various businesses to greet the staff and owners.
Mr Johnson briefly visited Ruislip Manor afterwards to see the illuminated bridge and some of the new businesses that have recently opened there.