After reports emerged on Friday that he had popped the question, the actor, 41, posted a sweet snap of the couple dating back to 2003, and addressed the speculation.
Jim Parson has denied on Instagram that he proposed to boyfriend Todd
"Me and Todd in 2003. Still very happy today... And NOT engaged! #justFYI," he captioned the picture.
The National Enquirer reported that Jim had proposed after his recent significant pay rise per episode for the hit comedy show.
A source reportedly told the American magazine: "The labour dispute had Jim really assessing where he was going with his life.
"Todd has wanted to get married for a long time now, and he told Jim he felt like they were just treading water in their relationship."
Jim and fellow cast members Kaley Cuoco and Johnny Galecki are thought to have signed new contracts which will net them a cool $1million per episode.
The three sitcom stars are now reportedly financially on par with the Friends cast, who are understood to have earned the same figure per show when the New York-based programme was in its final season.
The revamped contracts mean Kaley, 28, and her co-stars Johnny, 39, and Jim, 41, have almost tripled their previous wage of $350,000 per instalment of the 30-minute programme.