Purpose The relationship between motivation at work and internal knowledge transfers (IKTs) is an important topic in the knowledge management literature, but evidence on the topic is contradictory. This study aims to analyze the mediating role of transactive memory systems (TMSs) in this relationship. Design/methodology/approach Data were obtained from 208 military knowledge workers (analysts) from a large European army. Findings The results indicate that intrinsic and identified motivation positively affect IKTs, although fully mediated by the TMS. Introjected motivation, in contrast, has only a slightly significant direct influence and external motivation has no significant effect. As individual motivation is insufficient to speed up knowledge transfer, this paper proposes the solution of implementing a TMS, which generates trust and improves coordination among group members. Originality/value This study’s originality stems from both its context and the problem tackled. The context analyzed is the military, a group that has received very little attention in the field of management and business. Individual motivation in job performance has also received little study in a military context and even less research has related individual motivation to IKTs. To supplement the scarcity of existing studies and resolve the possible difficulties identified concerning IKT in the military, this study proposes to analyze the mediating effect of a TMS on the relationship between individual motivation to perform one’s job and IKTs.