Dressed in a personalized Mets jersey, the mayor, a Red Sox fan, was loudly booed throughout the stadium where he attended Opening Day along with other politicians and high-ranking members of the NYPD.
He was also booed at last year's Opening Day, where he threw out the first pitch — a strike, according to reports.
“It’s mayoral tradition to be booed on opening day and it wouldn’t be New York baseball without it,” a mayoral spokesman said in a statement.
The mayor did not speak with reporters after the game and hurried out of Citi Field as the first inning began.
The event was a solemn introduction of the baseball season as 150 police officers from the 84th and 79th precincts carried out a large American flag in the outfield and unfurled it as the National Anthem was sung.
Earlier in the day, the Ramos and Liu family spoke with reporters about how the Mets organization took them in after the Dec. 20, 2014 assassination of the officers in Brooklyn.
The Mets flew the families down to spring training in Florida and everyone from the top office to the players had treated them "like family," they said.
Pei Xia Chen, the newlywed wife of Det. Liu, said she hadn't seen her in-laws smile until they were down in Port St. Lucie this winter watching the Mets.
“We are so happy to be here at Mets Opening Day,” she said.
Chen, along with Det. Ramos' sons Justin and Jaden, threw the first pitch to players David Wright, Matt Harvey and Curtis Granderson in Queens before they took on the rival Phillies.
“They’ve been amazing with my children,” said Ramos' widow, Maritza. Her husband, who grew up in Brooklyn and Queens, was a "great Mets fan," she said.
“I just wish my husband was here to see it," she said, then added, "Let's go Mets!"