Government legislator Charrandass Persaud said: "I voted with my conscience."
The main opposition People's Progressive Party (PPP) said it was emboldened by the coalition's poor showing in November's midterm elections. The PPP picked up several seats in places that had recently been a stronghold for parties that form part of the political alliance known as A Partnership for Unity.
The vote now means that elections will have to be held even though Granger still has nearly two years left in his constitutional term.
The country is also about a year away from becoming an oil producer.
Clearly stunned by the development, legislators openly persuaded Persaud to vote with the combined APNU-AFC coalition, which holds 33 seats in the country's National Assembly to the PPP's 32. He stubbornly refused, saying: "Yes, yes, yes," when asked if he was siding with the opposition. He was escorted out of the chamber by police and allowed to leave through a back entrance after voting.
Opposition leader and former President Bharrat Jagdeo said Persaud might have been impacted by the layoff of about 7,000 sugar workers from the area where he lives and practices as an attorney.
Moses Nagamootoo, who is prime minister and head of the assembly, said that there may be outcomes "which have not been anticipated, but the outcome has to be accepted."
Nagamootoo said the government wanted supporters to know that the coalition would make another run in fresh elections.
"This is not the end," he said.