The incident allegedly happened just before 4 p.m. on Tuesday, May 21, at Dun Rite Upholstery on Jericho Turnpike in Syosset.
Police say the owner, 54-year-old Alfred Balcerak, of Freeport, approached a male employee in his 20s, pulled down his pants and grabbed his genitals.
The victim turned away, exited the store's warehouse and contacted police.
Balcerak, a Level 3 sex offender, turned himself in Tuesday without incident.
He is charged with first-degree sexual abuse.
In 2008, Balcerak allegedly fondled two young boys, ages 13 and 14, at a Bellmore upholstery store. In that incident, one of the boy's mother tracked Balcerak down using the sex offender registry website. He was convicted and served two years in jail.
Balcerak was convicted of sexually assaulting a 9-year-old girl and a 14-year-old back in 1998. In that instance, he only served probation.