East Windsor police say the reptile had to be removed from a resident's vehicle on Thursday.
Police wrote in Facebook post that it "was not exactly the call" they were expecting on the July Fourth holiday. Later, they said: "This may surprise you but we, the police, are not normally in the business of wrangling snakes."
The reptile was put in a crate and will be turned over to a nature center.
Police said the snake might have been a boa constrictor and speculated that it was an escaped pet. They tried calling an animal control officer or another expert, but none were available because of the holiday.