This study was to investigate how junior and senior teachers' perceptions of the Technological Pedagogical Content Knowledge-Games (TPACK-G) differ and how their TPACK-G perceptions predict their acceptance of game-based learning. 376 in-service elementary school teachers in Taiwan were invited to answer the TPACK-G and acceptance of game-based learning questionnaires. The results show that junior elementary school teachers tended to have higher GK, GCK and GPCK than the senior. Junior elementary school teachers' GPCK directly predicted their Attitude and Actual teaching usage, though none of the predictions were significant for the senior. Finally, the senior elementary school teachers' GK had negative relation to their Actual teaching usage.