Organizations rely on their employees to produce many high-quality ideas for the improvement of products, processes, and strategies. Evaluators such as managers and technical experts need to not only assess these ideas but also face expectations to contribute ideas of their own. We investigate this task duality by asking how idea evaluation activities affect evaluators’ ideation performance. Although much of the creativity and innovation literature points to a crowding-out effect, some theoretical arguments support idea crowding-in. Using data from a multinational firm’s idea management system and a difference-in-differences framework, we find robust evidence of substantial idea crowding-in: Evaluators’ likelihood of idea generation increases by 205% on the day that they evaluate ideas and remains elevated for the following two weeks. Extensive analyses support knowledge recombination as the key mechanism: By exposing evaluators to unfamiliar knowledge, idea evaluation creates new opportunities for recombination and idea generation. The ideas that evaluators generate postevaluation are 19% more valuable (but not more novel) than those they generate outside the postevaluation window. We contribute to innovation scholarship by identifying a hitherto overlooked effect of idea evaluation: triggering idea generation among evaluators. This paper was accepted by Karan Girotra, operations management. Funding: J. Schnier and C. Raasch acknowledge funding from the Deutsche Forschungsgemeinschaft [Grant RA 1798/4-1]. T. Schweisfurth acknowledges funding from the Tempowerk Technology Center Hamburg. Supplemental Material: The online appendix and data files are available at https://doi.org/10.1287/mnsc.2023.03335 .