Studies show that experiencing traumatic events can lead to positive psychological change, or posttraumatic growth (PTG). In the hope of promoting PTG, authors have been focusing on identifying the factors that may foster PTG. Despite these attempts, the literature shows inconsistencies, making it difficult to know which variables may be involved in the process of growth. Indeed, authors seem to disagree on the nature of the relationship between PTSD and PTG, time since the event, social support, intrusive rumination, and sociodemographics. Thus, this study aims to clarify these discrepancies, and verify whether the processes involved are the same across two different cultural groups, both of which are confronted with traumatic events regularly: 409 American firefighters, and 407 French firefighters. Results indicate that, in both samples, PTG is positively related to PTSD, subjective perceptions of the event, stress during the event, disruption of core-beliefs, and deliberate rumination; and unrelated to social support, core-self evaluations, and socio-demographic variables (age, gender, relationship status, etc.). However, time since the event and the number of years on the job only predicted PTG in the American sample, while colleague and emotional support only predicted PTG in the French sample. Additionally, American firefighters reported more growth, more social support, more positive self-perceptions, more intrusive rumination, and more neuroticism than French firefighters. These results suggest that the process of growth, as defined by Tedeschi and Calhoun, is relatively stable among firefighters, but that some differences do exist between cultural groups.