The 71-year-old actor has signed the same contract as the show's other five primary voice actors: Hank Azaria, Dan Castellaneta, Nancy Cartwright, Julie Kavner and Yeardley Smith.
The two-season deal pays an estimated $300,000 US per episode and includes an option for another two seasons. Fox has renewed the show for a historic 27th and 28th season, with a 29th and 30th considered likely.
Shearer, a member of the cast since it was just a cartoon short on The Tracey Ullman Show, sparked a massive online furor in May with his announcement he was leaving the popular program over a contract dispute.
His vast roster of characters for the show included elementary school principal Skinner, broadcaster Kent Brockman, Springfield elders Dr. Hibbert and Rev. Lovejoy, as well as bus driver Otto and Homer's pal Lenny.
At the time via social media, Shearer cited "the freedom to do other work" as the reason behind his decision to leave.
However, in various interviews, Simpsons showrunner Al Jean revealed that everyone in the cast tackles additional projects and that producers have never prevented anyone from pursuing other work.
Though Shearer has not yet commented about his return, the official Simpsons Twitter account revelled in the news.
The 27th season of The Simpsons debuts on Sept. 27.