Trucks from the health department fanned out repellent across Manhattan overnight to target the insects.
City officials say the number of mosquitos with West Nile virus is up this summer and this will help reduce transmission.
There have been six confirmed cases in the city so far this summer.
The city's first spraying session started around 8:30 p.m. Monday and was expected to wrap around 6 a.m. Tuesday.
The health department targeted tUpper Manhattan, Central Park and the Upper East Side.
While the health department says most people with West Nile virus show no symptoms, the disease can be concerning for people over 60-years-old or with weakened immune systems.
Symptoms include fever, headache and vomiting.
Crews will start spraying in southwest Brooklyn beginning 8:30 pm on Wednesday.
They will be targeting areas between 3rd Avenue and Ocean Parkway and between 65th Street and Coney Island Beach and Gravesend Bay.
Meanwhile, New Yorkers say they are happy the city is doing something to stop the spread of mosquito-borne diseases.
"I think its great that they're taking a proactive approach and getting rid of the mosquitos. I did not know that there was West Nile, but I'm happy they're doing something about it," a parkgoer told Eyewitness News.
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