The £3 million property, owned by the ‘The Club is Alive’ singer, was badly damaged during the two-and-a-half hour blaze, which police are treating as suspected arson.
Ten fire engines and 70 firefighters amassed at the fire at the “derelict property” in Croydon, south London, on Tuesday.
Williams appears to have moved out of the property, which was in a state of disrepair before the fire, but it was once home to late TV comedian Ronnie Corbett.
Part of the first and second floor of the detached three-storey home was burnt and a small part of the roof was also damaged.
The London Fire Brigade confirmed that they were called at 4.30pm – but the fire was under control by shortly before 7pm.
Crews from eight local stations fought the blaze.
Former JLS star Williams, 32, was cleared on May 28 by a jury of attacking a fan in a hotel room after a solo gig back in December 2016.
Photos of the home revealed broken windows and a green pool in November.
A spokeswoman for Scotland Yard has confirmed that that “arson form a line of enquiry” in their investigation.
She said: “Police were called at 4.39pm on Tuesday, June 4 following reports of a fire at a residential address in Spout Hill, Croydon.
“Officers attended with LFB. There were no reported injuries. There have been no arrests.
“The fire is being treated as suspicious and therefore it will form part of enquiries as to whether it is a case of arson. Enquiries underway as to cause of fire.”