Background: The shortage of nurses is a global problem. Increasing the level of work engagement is known to effectively reduce turnover rate among nursing staff. Strategies to improve work engagement based on the job demands–resourcesmodel may effectively improve nurses' job satisfaction and reduce staff turnover. Purpose: A job demands–resources model was used in this study to test the hypothesis that work engagement is affected by both external resources (professional nursing practice environment) and internal resources (self-efficacy and achievement motivation). In addition, the mediating role of self-efficacy and achievement motivation in the relationship between professional nursing practice environment and work engagement was also verified. Methods: A cross-sectional survey employing a convenience sampling design was implemented. Five hundred fifteen registered nurses were recruited from four tertiary hospitals in Chengdu, China, fromJanuary to June 2020. The Practice Environment Scale of the Nursing Work Index, General Self-Efficacy Scale, Achievement Motive Scale, and Utrecht Work Engagement Scale were used to measure the four variables. Results: The results of the structural equation model showed that the degree of fit for each index model was good, indicating that all of the three variables, including professional nursing practice environment, self-efficacy, and achievement motivation, directly affected work engagement. In addition, the variable professional nursing practice environment was found to indirectly influence work engagement through the partial mediation of self-efficacy and achievement motivation. Conclusions: The resultsmay be used to guide health policymakers and nurse managers attempting to enhance the work engagement of nurses by providing a supportive working environment, improving the welfare mechanism, formulating a talent training plan, and fostering appropriate empowerment to improve the working environment, self-efficacy, and motivation in nurses.