The purpose of this paper is to investigate the effects of knowledge sharing methods on firms’ innovative performance. In particular, this study divides knowledge sharing methods into OJT as an interpersonal way at the individual level and organization learning as a systematic way at the organizational level, and predicts these ways will increase innovative performance in the small-medium enterprises. In addition, this study considers these main effects can be different depending on the orgnizational contexts, and examines the moderating roles of aging workforce and age diversity. This study hypotheses that the high percentage of aging workforce as well as the high level of age diversity will strengthen the relationship between knowledge sharing methods and firms’ innovative peformance because these organizations are more needed to transfer tacit knowledge into explicit knowledge. To test these hypotheses, this study uses the Human Capital Corporate Panel datasets collected by KRIVET. The analytical findings showed that OJT as well as organization learning positively influenced firms’ innovative performance, but the effect of organization learning was only statistically significant. Moreover, in the cases of moderating effects, whereas the effect of organization learning on firms’ innovative performance was stronger when the percentage of aging workforce was relatively high, the effect of organization learning on firms’ innovative performance was rather weaker when the level of workforce diversity was relatively high. In the conclusion part, this study suggests academic as well as practical implications and limitations for future research.