Objective: To prevent transmission among the staff and potentially among the non-human primate (NHP) colony at the U.S. Naval Medical Research Center Detachment in Peru, where an active case of mumps was discovered in a senior laboratory technician in Sep 03, 2007. Material and Methods: Subjects at the research facility were interviewed and potentially susceptible contacts were tested for mumps IgG. Results: In total, 81 out of 106 staff members (76%) had close contact with the case. Only 6/81 (7%) had MMR, 33 (41%) reported having had mumps, and 8 of 45 (18%) of the potentially susceptible individuals did not have immunity (IgG > 20.0). All the susceptible, exposed individuals received MMR vaccine. There were no secondary cases and access to the NHP colony was restricted. Discussion: Immediate and thorough investigation and occupational health response were imperative in preventing secondary cases of mumps among humans and NHP.