The present study investigates the possible mechanisms involved in the link between daily job crafting and daily work engagement. Using self-determination theory, we hypothesize that daily job crafting is positively related to daily work engagement through momentary need satisfaction and momentary engagement. Additionally, using self-regulation theory, we predict that daily job crafting is negatively related to daily work engagement, through momentary energy depletion and (reduced) momentary work engagement. Participants from various occupational sectors (N = 66) responded to a daily diary questionnaire (N = 261) as well as momentary, task-related items (N = 1539) using a day reconstruction method at the end of each of four working days. Th...