Police released a sketch of one of the suspects.
They say he's one of four black teens who attacked the 39-year-old Hispanic man while he was walking along the bridal path, near the reservoir, at East 95th Street and East Drive just after 5 p.m.
They reportedly struck the victim with a metal water bottle, then knocked him to the ground and kicked him before stealing his cash.
The victim was not seriously hurt.
The suspects fled south into the park.
The first suspect, who grabbed the victim and threw him to the ground, is described as around 17 years old, approximately 6-foot-1 with a medium build, short hair and a light mustache, wearing a white T-shirt and shorts.
The three other suspects are all described as 14-17 years old, wearing white T-shirts.
Anyone with information in regard to this incident is asked to call Crime Stoppers at 1-800-577-TIPS (8477). You can also submit tips by logging onto the Crime stoppers website at WWW.NYPDCRIMESTOPPERS.COM or by texting tips to 274637 (CRIMES) then enter TIP577. All calls are strictly confidential.