Background: The results from past studies about the effects of second-generation e-prescribing systems on community pharmacists' outcomes and practices are inconclusive, and the claims of effectiveness and efficiency of such systems have not been supported in all studies. There is a strong need to study the factors that lead to positive outcomes for the users of these systems. Objective: This paper intends to bridge the above gaps by empirically examining the impacts of user interface usability on the community pharmacists' outcomes. Methods: A quantitative survey research method was used and the data was collected from the community pharmacists, who use an e-prescribing system. Data from 152 questionnaires collected in a national survey were used to for the study. Partial Least Squares (PLS) path modeling was used to examine scale reliability, validity and hypotheses. Results: The scale was found to test well for reliability and validity. Examining the hypotheses illustrated that ease of use (P<0.01, t=5.79) and information quality (P<0.01, t=6.24) of an e-prescribing system improved pharmacists' outcomes (including communication, facilitation of care, reduction of workload and medical errors) while ease of use of the system was influenced by user interface consistency (P<0.01, t=7.35) and system error prevention (P<0.01, t=5.29). Conclusion: To improve community pharmacists' outcomes and practices, the ease of use, information quality, consistency and error prevention features of e-prescribing systems should be improved. It was found that information quality had a stronger impact on the outcomes and hence improving the quality of the generated information would have higher impacts on users' outcomes.