A city Parks Department worker was sexually assaulted this morning at a playground in Brooklyn, police said.

The 29-year-old employee was attacked inside a park shed at St. Andrew’s playground at about 9 a.m. near the intersection of Atlantic and Kingston avenues in Bed-Stuy.

The attacker — a black male in his 30s standing about 5-foot-9 — covered the woman’s mouth and used a box cutter to scare her, police said.

Another park worker walked into the facility, which houses offices and bathrooms, during the attack.

The attacker then fled on a bike.

The victim was taken to Kings County Hospital.