Hamilton and Mercedes were off the pace throughout as the seven-time world champion finished seventh while Valtteri Bottas failed to complete the race at the principality.
It leaves Hamilton now four points shy of Verstappen, who proved a class apart on the street circuit.
“We definitely can’t afford another weekend like this,” said Hamilton in the aftermath. “But I’m grateful I’ve finished and grateful I got some points, fastest lap.”
The Ferraris looked to have the ultimate pace but polesitter Charles Leclerc failed to get over the start line while teammate Carlos Sainz had to make do with second place behind Verstappen.
A frustrated Hamilton, who had won three of the previous four races, lacked pace all race but was also undone by a failed Mercedes pitstop strategy.
Looking ahead to the rest of the title fight, Hamilton added: “It’s going to be tough. I told you at the beginning, they’ve got a championship-winning car, and they’re going to be very hard to beat.
“I’ve been serious about it all year. We’ve won races which we shouldn’t have won, like in Bahrain. But it’s not over. There’s a long, long way to go.”
Quite how vital Hamilton’s points haul, however minor, proves to be for the rest of the season remains to be seen.
The 36-year-old said the team would be working “flat out” in the coming days to get to the bottom of understanding their lack of speed compared to the likes of the Red Bulls, Ferraris and even McLarens in Monaco.
Despite a near-perfect weekend, Verstappen warned that Mercedes remained the team to beat at the more standard F1 circuits.
“There is a long way to go,” he said. “We will have to work hard because we know that Mercedes on normal tracks are the ones to beat.”