What critical factors contribute to knowledge workers' effective information management and consequent job performance? This paper begins to address this important question by developing a conceptual definition of a new construct called personal information management effectiveness (PIME) and its constituent dimensions. Specifically, we theorize that PIME consists of two underlying dimensions: personal information management motivation (PIMM) and personal information management capability (PIMC). Synthesizing the extant literature on information management and information orientation, we further conceptualize PIMM as having four sub-dimensions of proactiveness, sharing, transparency, and formality, and PIMC as possessing five sub-dimensions of sensing, collecting, organizing, processing, and maintaining. Moreover, we develop a theoretical model that positions PIME as a mediator between two selected individual characteristics (IT self-efficacy and need-for-cognition) and job performance. New measures for PIME dimensions were developed and shown to have strong psychometric properties. The proposed model was empirically tested using data collected from 352 knowledge workers. As theorized, PIME was found to have significant effects on job performance (41%) and fully mediate the effects that the selected individual characteristics have on job performance. Responding to recent calls for advanced research on personal information management, the measures of PIMM and PIMC developed in this study have practical value as research and diagnostic tools and the findings provide useful insights to help organizations improve knowledge workers' information management practices.