Video shot by the boy's mother shows a dozen or so men in the Furn El Chebbak neighbourhood of Beirut, the Lebanese capital, belting out the earworm tune that has bewitched children and bedevilled parents around the globe.
Robin, the toddler, looks on as protesters carrying Lebanese flags surround the car and perform the song's signature clap.
One of the men in the video, Elie-joe Nehme, told NBC News via Facebook Messenger that he and other protesters were yelling and clapping as they marched alongside some cars during a road closure on Saturday. Then a woman nearby told them to be quiet because of the noise bothering baby Robin.
"So we sang 'Baby Shark' to make him happy," said Nehme, 22.
The boy's mother, Eliane Jabbour, told NBC News her 15-month-old was "surprised but not afraid" to hear a rowdy rendition.
The episode was a short reprieve from days of unrest that saw hundreds of thousands of people flooding the streets across the country.
Protesters have accused the political elite of looting the economy to the point of collapse and are demanding regime change.
In a bid to ward off crisis and defuse protests, the government approved an emergency reform package on Monday.
Nehme said he and others went back to protesting after the cheerful encounter with the toddler.
"There's a revolution happening here in Lebanon," he said.
Nehme, who has been part of the protests since they began on Thursday, said they are hoping the demonstrations will achieve "a better Lebanon."
Paul Ziad Nassar contributed to this story.