Employees' knowledge is a critical resource for the organization, and if it is not shared, it is lost to other employees and the organization. However, knowledge sharing (KS) does not happen easily; KS is a personal choice that cannot be forced. This study employs Self-Determination Theory (SDT) as a theoretical framework to study employees' KS behavior and motivations. Data were collected from full-time working professionals (N=208) using an online survey. The effects of autonomy, motivation, trust, authentic leadership style (ALS), knowledge self-efficacy, and technology were studied using moderated and mediated regression analyses. The results reveal (a) knowledge is shared more when individuals have more autonomy; (b) benevolence-based and institution-based trust had a moderating effect on autonomy and KS behavior (when autonomy was low, if benevolence-based or institution-based trust was high more KS occurred); (c) competence-based trust did not have a similar moderating effect, but had a significant main effect predicting KS; and (d) a supervisor's ALS contributed in explaining the total variance of KS behavior and predicted KS after controlling for autonomy. All three types of trust mediated the relationship between ALS and KS. Moreover, knowledge self-efficacy is a strong predictor of KS, while users' perception of technology is a moderate predictor. Additionally, a factor analysis was conducted on 15 different types of KS technologies used by participants. Technologies were clustered into three groups based on their degree of interactivity. Only high-interactive technologies positively correlated with trust predicted KS. This study advances prior findings and contributes to KS research and practice. It was the first to examine relationships between ALS and KS, proved that SDT is a strong framework in predicting KS motivations, and showed only high-interactive technologies positively linked with trust predict KS. Organizations could use these findings to develop appropriate strategies and trainings to foster a KS environment.