A “Let’s go Brandon” sticker and another anti-Biden decal were spotted on the back of a Philadelphia police cruiser — and authorities are investigating how they got there.

The coded phrase favored by critics of the commander-in-chief — which actually means “F–k Joe Biden” — was noticed by an eagle-eyed Philadelphia woman Thursday. The other sticker on the back of the police cruiser left nothing to the imagination.

“So @PhillyPolice cars are allowed to have f–k joe biden stickers now?” Arielle Klagsburn tweeted, tagging the city’s police commissioner, mayor and district attorney in the process.

The post, which was retweeted 160 times as of Friday, caught the attention of Philadelphia police officials some 40 minutes later.

“Thank you,” department officials replied. “We are aware of the contents of this image and an investigation into this incident is underway.”

No “further information” was available Friday, a Philadelphia police spokesman told The Post when reached for comment.

Cops told the Philadelphia Inquirer Thursday it was unclear who was behind the offending stickers.

Klagsburn, meanwhile, said she saw the police cruiser in South Philadelphia as she was driving.

“I was pretty surprised,” she told the Inquirer. “We know obviously there’s a lot of forces within the police who tend to wear their politics on their sleeve … [but] I was surprised the police department would allow anyone to put their personal political views on a vehicle funded by taxpayers.”

Some Biden detractors on Twitter claimed “every vehicle” should be emblazoned with such stickers, while others suggested simply removing them and moving on in a city that has set an all-time homicide record in 2021 with 524 killings as of Thursday, according to police department data.

“Over 500 murders in Philadelphia but don’t let that distract you from important stories like this,” one commenter shot back.

Others surmised the stickers were likely placed on the rear of the police cruiser by some “random” person.

A police spokesman did not respond to an inquiry Friday as to whether there’s any evidence an officer was involved.

At least 12 major US cities set new annual homicide records this year, including Indianapolis; Louisville, Kentucky; Austin, Texas; Rochester, New York; and Portland, Oregon, according to ABC News.

Homicides nationally surged roughly 30 percent in 2020 compared to the previous year, FBI data shows — the largest one-year increase since the law enforcement agency began keeping records six decades ago.

Chicago, the nation’s third-largest city, is leading the country in the grim statistic, with 739 homicides as of the end of November — a 3 percent increase from 2020, according to police data obtained by ABC News. The city’s all-time record of 974 homicides was set in 1970.