Codesign allows a design team to combine two sets of knowledge that are key to service design: Customer insights into latent user needs and in-house professionals’ conversion of promising new ideas into viable concepts. While some studies highlight the potential of codesign, others are more skeptical pointing to a lack of clarity over how the involvement of customers affects the design process and outcomes. This article addresses this knowledge gap by reporting on a real-world comparison of design concepts generated by codesign teams with those generated by an in-house professional team and a team solely made up of users in the course of a library service ideation contest. The comparison indicates that codesign teams generate concepts that score significantly higher in user benefit and novelty but lower in feasibility. However, these outcomes are only possible in cohesive teams that develop design concepts collaboratively. In contrast, in teams where individuals dominate, conflict, less collaboration, and diminished innovation outcomes are more likely. The findings add to a better understanding of the value of codesign and shed light on the complex relationship between design team composition, intrateam factors, and innovation outcomes. Service designers obtain recommendations for selecting customers, assembling teams, and managing intrateam dynamics to enhance codesign success.