The Cardinals (31-37) racked up 12 hits on the night, and Dariel Gomez was a big contributor, going 3-for-4 with two doubles and two RBIs.
Andrew Warner and Brian Sanchez each had two hits for Johnson City.
Liam Sabino had a two-run home run in the bottom of the third that gave the Cardinals a 3-2 lead.
Juan Alvarez (3-2) was the victorious pitcher for Johnson City, while Liam McCall (0-2) took the loss for the Mets.
Ronny Mauricio and Yoel Romero each had two hits and scored a run for the K-Mets (33-35). Romero led off the game with a home run and had two RBIs.
The K-Mets will host the Appalachian League West Division champion Elizabethton Twins on Friday at 6:30 p.m. for the first of a three-game set. The final two games will be in Elizabethton on Saturday and Sunday. Both games are slated to begin at 6:30 p.m.
The winner of the series will advance to the Appalachian League Championship Series.