Most studies of worker participation examine either formal participatory structures or informal participation. Yet, increasingly, works councils and other formal participatory bodies are operating in parallel with collective bargaining or are filling the void left by its decline. Moreover, these bodies are sprouting in workplaces in which workers have long held a modicum of influence, authority, and production- or service-related information. This study leverages a case from the healthcare sector to examine the interaction between formal and informal worker participation. Seeking to determine whether or not these two forces—each independently shown to benefit production or service delivery—complement or undermine one another, we find evidence for the latter. In the case of the 27 primary care departments that we study, formal structures appeared to help less participatory departments improve their performance. However, these same structures also appeared to impede those departments with previously high levels of informal participation. While we remain cautious with respect to generalizability, the case serves as a warning to those seeking to institute participation in an environment in which some workers have long felt they had the requisite authority, influence, and information necessary to perform their jobs effectively.