Michael Barrymore has been arrested along with two other men over the death of Stuart Lubbock.
Michael Barrymore, 55, has been arrested by Essex Police
Mr Lubbock, 31, was found by the swimming pool at the TV star's house near Harlow, Essex, in March 2001.
Mr Barrymore, 55, and two men, aged 37 and 32, have been arrested on suspicion of serious sexual assault and murder.
Essex Police said the 37-year-old man had been arrested in Lancashire and the 32-year-old man was taken into custody in north Staffordshire.
Mr Lubbock had been among a number of people at a party at Mr Barrymore's home in Roydon in the hours before his body was found.
An inquest into his death recorded an open verdict after hearing he had also suffered severe internal injuries which suggested sexual assault.
Alcohol, ecstasy and cocaine were found in his bloodstream.
An investigation was carried out by Essex Police after Mr Lubbock's body was found, but no-one was charged with any offence in connection with his death.
Stuart Lubbock's body was found by the side of the swimming pool
In December 2006, Essex Police began a new inquiry.
The Independent Police Complaints Commission (IPCC) also launched an investigation.
Following the arrests, the IPCC said it had placed on hold its inquiry into complaints from the family arising from the original Essex Police investigation.
Mr Lubbock's father, Terry, 62, of Harlow, said: "I've been in limbo for the past six years. My life has been on hold. I will never get those six years back again. Why has it taken so long?
"I have had so many disappointments over the past six years. This could be another one. I am waiting for the jackpot. I am waiting with bated breath.
"I am going to keep on going. I am not going to let my son down, no matter how many disappointments."
He said police had given him no warning of the arrests.
He said when he was told of the arrests he "did not explode with any excitement or anticipation, as I have been let down in the past".
Mr Lubbock's brother, Kevin, 39, also of Harlow, added: "I am really happy this has all come to light. It's been a long time... I am a bit numb."
Terry Lubbock's lawyer, Tony Bennett, said: "What we've been campaigning for over the past 18 months is for somebody to be charged and brought to court."