Job Crafting has been proposed as a new perspective, consisting in a bottom-up strategy to achieve person–job fit by emphasizing employees’ active participation and spontaneous change in job design, which is specifically adequate for older workers. Despite this fact, the cyclical influence between Work Engagement and Job Crafting over time has been less researched. We postulated that a gain cycle could be observed in the relationships between Job Crafting and its outcomes. Hence, we tested a longitudinal moderated mediation model in which Work Engagement increases over time through an increment in Job Crafting behaviors (Hypothesis 1), while this process is moderated by workers’ age (Hypothesis 2). The present study follows a three-wave design where participants (N = 126) responded to online surveys at three measurement waves, three months apart. At Time 1 and Time 3, we assessed Work Engagement, Job Crafting behavior, and demographic variables, while at Time 2 we only assessed Job Crafting. Our findings partially differ from what was expected. The findings supported that the relationship between Work Engagement at Time 1 and changes in Job Crafting behavior across time was negative and non-significant, failing to provide support for Hypothesis 1. Related to Hypothesis 2, our results are mixed. Although the interaction between changes in Job Crafting and workers’ age did not demonstrate a statistical influence on Work Engagement at Time 3, our findings suggested that the direct influence was complemented by a negative indirect effect through the longitudinal increase of Job Crafting, which mainly affects aged workers. Practical and theoretical implications are discussed. © 2022 by the authors.