Mejia returned July 7 from an 80-game suspension that began in April for using a performance-enhancing drug. The latest suspension involved a positive test for Stanozolol and Boldenone, which are both considered PEDs, and begins immediately.
The ban is the longest for performance-enhancing substances in MLB history, matching Alex Rodriguez's 162-game suspension last season. Meija is the first major leagueer to fail two PED tests.
The 25-year-old Mejia had pitched 7 1/3 scoreless innings of relief this season in a setup role, allowing four hits and two walks with seven strikeouts.
Last year, Meija posted 28 saves and had a 3.65 ERA for the Mets.
"We were extremely disappointed when informed of Jenrry's second suspension for violating Major League Baseball's Joint Drug Prevention and Treatment Program," the Mets said in a statement. "We fully support MLB's policy toward eliminating performance enhancing substances from the sport."
On Monday, the Mets acquired reliever Tyler Clippard from the Oakland Athletics to help their bullpen.