The fire broke out at the old Laser 20 building opposite Morrisons in the early hours of Sunday morning.
West Midlands Fire Service said it was called to the derelict two-storey building in Upper Lichfield Street at around 1.55am.
The fire started in the ground floor of the building which has been empty since the laser centre closed in 2016 amid allegations of child grooming.
The cause of the blaze has not yet been confirmed but firefighters, who were at the scene for around two hours, alerted police to the incident.
A spokesman for West Midlands Fire Service said: " We were called at 1.55am on Sunday to a fire in the ground floor of a detached two-storey derelict commercial building measuring in 30 by 15 metres in Upper Lichfield Street, in Willenhall.
"Crews from Willenhall, Bilston, Walsall and Fallings Park stations attended the scene. We made checks on both floors of the building and we also requested the police to attend.
"The building was previously was used as a laser quest facility.
"Our last crew left the scene at around 4.10am."
A West Midlands Police spokesman said: "We were notified of the fire by the fire service. We will be making enquiries to find the owners of the property."
Anyone with information can call West Midlands Police on 101, quoting incident number 670 of May 30.