He had earlier been spotted getting out of his helicopter which had landed on the green at Penn Golf Club before putting in an appearance at The Mount Tavern on Penn Road, where he enjoyed an ice cold pint and chatting to punters.
Mr Johnson was accompanied by the Mayor of the West Midlands, Andy Street.
Pub manager Melissa Nicholls, said she was expecting to see Mr Street but not the Prime Minister, adding that the customers were also very surprised as he made his entrance.
It did not take long for the PM to get behind the bar himself, pulling a pint of Timothy Taylor's Landlord, which he then drank.
Punters in the Penn Road pub's beer garden enjoyed a socially distanced drink with the Prime Minister, with some even getting selfies to commemorate his unexpected visit.
Melissa, who has worked at the Mount Tavern for seven years and is now the manager of the pub, was surprised when the Prime Minister walked through its doors.
She said: "It was a real surprise when the Prime Minister arrived at the pub with our Mayor Andy Street.
"We were expecting to welcome our Mayor Andy Street, however the PM’s arrival was a complete surprise. This was his first visit to the Mount Tavern.
"Customers were surprised to see the Prime Minister at the pub, but the atmosphere was as great as it has been all week, everyone is really happy to be back at the pub.
"We were happy to welcome him behind the bar to pull his first pint since the reopening of pubs and chat with them both.
"He chatted with customers about how great it was to be back at the pub, as well as the vaccine programme where he asked some customers whether they have had any of their vaccinations yet.
"Mr Johnson was very happy to be in the pub, and to meet and see guest safely reconnecting.
"Over the past week it has been fantastic to see so many people safely coming back together, reuniting at the pub and we’re really pleased the Prime Minister got to witness this first hand.”
Mr Johnson stayed for one drink, before leaving The Mount Tavern to get back to work.
His visit came ahead of the West Midlands' mayoral election next month.