Six different crews tackled the fire at the derelict 18th Century Wheaton Aston Old Hall building in South Staffordshire.
The A5 at Watling Street at Ivetsey Bank was closed in both directions as they tackled the blaze.
Formerly known as Utopia, the swingers club was a popular adult venue for couples.
A spokesperson for Staffordshire Fire service said: "We were dealing with a severe building fire in Ivetsey Bank.
"It was quite a large blaze.
"We received a call at 11.20pm on Monday.
"There were six pumps in operation at the height of the blaze from fire engines from over the county."
A fire investigation officer is conducting checks at the scene.
The spokesperson said they are working to confirm the cause of the fire.
A fire previously broke out at the building in April this year.