Introduction: Crew performance in space has become an increasing focus due to the recent shift towards longer-duration human space missions to the Moon and Mars. Past expeditions carried out on Earth kept records of crew performance, which have been compared and analyzed to those reported on space missions. Purpose: This study investigates crew psychosocial group functioning through an analysis of group environment, stress, and coping data, while looking at the relationship of this data to overall crew performance. Methods: A six person heterogeneous American crew conducted a Mars simulation mission at the Mars Society's Mars Desert Research Station in Utah, USA in 2006. Participants were administered pre-mission assessments of personality, stress and coping, and personal motivation and orientation. Personal mission mistakes and Habitat problems were reported daily by each crewmember to the crew psychologist. Mid-and end-mission assessments were administered to measure cognitive functioning; group functioning/identity; perceived stress and coping; and personal motivation and orientation. Results: The overall analysis indicated effective performance and positive coping with regards to the heavy workload and environmental stressors the crew experienced. A relationship also existed between the psychology assessment data obtained and mistakes reported daily by the crew.