Entertainment Weekly claims the series network, CBS, was trying to negotiate two more season, however, Jim Parsons - who plays Sheldon Cooper - made the decision to walk away.
EW adds the updated two-year deal would see each cast member secure $69 million if agreed, however, Parsons was "ready to say goodbye."
The Big Bang Theory made the actor, along with his four original co-stars Kaley Cuoco, Johnny Galecki, Kunal Nayyar, and Simon Helberg, a household name. With a reported salary near $1.4 million per episode, the 45-year-old also won four Emmys and one Golden Globe for his lead role in the series.
In a joint statement confirming the shows finish, WBTV, CBS and Chuck Lorre Productions said: "We are forever grateful to our fans for their support of The Big Bang Theory during the past 12 seasons.
"We, along with the cast, writers and crew, are extremely appreciative of the show’s success and aim to deliver a final season, and series finale, that will bring The Big Bang Theory to an epic creative close."