This study examines coordination processes (transactive memory) among humanitarian aid workers, and the relationships between stress, social support and transactive memory. Sixty humanitarian aid workers from non-governmental organisations completed a questionnaire. The measures included scales of transactive memory, perceived stress, compassion fatigue and social support. Data from partial least squares (PLS) showed that transactive memory is not structured identically among stable teams and humanitarian aid teams: transactive memory is essentially based on tacit coordination processes among humanitarian aid workers. The results showed that stress was negatively related to transactive memory and that social support was positively related to it. Moreover, social support was not a moderator of the relationship between stress and transactive memory. This study highlights the need to develop programmes to prepare humanitarian aid workers for the management of emergency situations and to protect them from stress.