Police said the 36-year-old's body was found by electricity workers at Kenthurst at 12:30pm Thursday and initial inquiries suggest no suspicious circumstances.

Robinson, a former Parramatta Eels and Sydney Roosters player, had not been seen since 7:30pm on November 26, when he left his house on Crestview Avenue in Kellyville in his silver Subaru Outback, police said.

Police at the time said there were "grave concerns for his welfare, and police urge anyone who sees him to contact them immediately".

Robinson's sister, Monique Brennan, said her brother did not have his phone or wallet with him.

Police said his car was discovered at the intersection of Marieba and Porters roads.

"While the man is yet to be formally identified, it is believed to be the body of a 36-year-old man who was last seen at his Kellyville home on Saturday 26 November 2016," police said in a statement.

"A post mortem examination will officially determine how the man died. Initial inquiries suggest there are no apparent suspicious circumstances."

Robinson, the older brother of Cronulla Sharks player Tim Robinson, made his NRL debut in 2000 and played 160 games for the Eels and Roosters.

In 2009 he joined English Super League side Harlequins, but was released from his contract after suffering a knee injury.