Based on the job crafting perspective, we theorized a serial curvilinear mediated moderation model that links underemployment to two outcomes that benefit the organization: creativity and organizational citizenship behavior. A three-waved time-lagged survey in teachers and a field study in technical workers provided convergent support of this model. In Study 1, using data from 327 teachers and their immediate supervisors, we found support for our hypotheses that perceived underemployment had an inverted U-shaped relationship with task crafting and that this relationship was moderated by organizational identification. When the teachers' organizational identification was high, they engaged in more task crafting for the organization at intermediate levels of perceived underemployment. We also found that task crafting was positively related to creativity and organizational citizenship behavior. In Study 2, the simulation tasks for 297 technical workers provided convergent evidence for that objective underemployment indirectly influence objective task crafting through perceived underemployment with the inverted U-shaped path from perceived underemployment to task crafting. We discussed the theoretical and practical implications of this research.