Investigators say 33-year-old Lucas Strada was making and selling anabolic steroids.
Steroids, lab equipment and packaging materials were found in his Centereach home.
He is accused of selling the drugs in person and online.
"On July 30, search warrants executed at his residence and to search his vehicle led to the discovery of mass quantities of anabolic steroids which we believe the defendant manufactured for resale," Suffolk County District Attorney Tom Spota said.
Spota said detectives also seized a loaded Rock Island Arms .45-caliber handgun from Strada's bedroom and more than $60,000 in cash from his vehicle.