Summary Issue: Child protection workers are repeatedly exposed to potentially traumatic events (PTE) in the course of their work, including acts of violence. As a result, they are likely to develop mental health problems such as anxiety, insomnia, depression and post-traumatic stress symptoms. The occupational consequences of PTE have high costs for the individual and the organization: reduced job satisfaction, absenteeism, job changes, lower productivity, etc. In this context, the Centre-Sud-de-l’Île de Montréal Child and Youth Protection Centre implemented a post-traumatic intervention protocol (PTI) involving a team of peer helpers trained to provide support to employees affected by a PTE. Study objectives: This study has four objectives: (1) to compare the effects of a PTI in conjunction with conventional support (i.e., support from coworkers and supervisors, referral to an employee assistance program) to conventional support alone on psychological symptoms and the occupational functioning of workers exposed to a PTE; (2) to identify the psychological status and occupational functioning predictors in workers exposed to a PTE; (3) to explore the reasons that workers exposed to PTEs underwent or did not undergo a PTI; and (4) to explore the support needs of workers exposed to a PTE. Methodology: The participants were workers from the Centre-Sud-de-l’Île de Montréal and the Monterégie-Est child and youth protection centres who had been recently exposed to PTEs at work. The vast majority of PTEs reported (96%) involved exposure to aggressive behaviours by youth or their parents. The participants completed a set of online questionnaires on four occasions: within one month of the PTE (176 workers), two months after the PTE (168 workers), six months after the PTE (162 workers), and 12 months after the PTE (161 workers). The questionnaires included measurements of gender roles, psychological symptoms, functioning at work and perceived support. Sixty-four participants also took part in individual interviews on their reasons for undergoing or not undergoing a PTI (for the Montréal participants) and on support needs. Results: For the first objective, the participants were divided into three groups: (1) the participants from Montréal who underwent a PTI; (2) the participants in Montréal who did not undergo a PTI; and (3) the participants in Monterégie-Est where no specialized post-traumatic peer-support program was offered. In Time 1, participants in the Montréal group with PTI and those in Monterégie-Est had more acute stress symptoms and a higher level of absenteeism than participants in the Montréal group without PTI, suggesting that they were more affected by their PTE. Regardless of the measurement time, there were no significant differences between participants in the PTI group and those of the two other groups for other mental health and occupational functioning variables. Overall, these results did not support the superiority of PTI plus conventional support compared to conventional support alone. With respect to the second objective, some potentially modifiable work variables predicted the severity of psychological symptoms, low work productivity and/or the quality of work life in the year following exposure to a PTE. In particular, confidence in their ability to cope with the aggressivity of clientele and the degree to which the job was perceived to be safe were protective factors, while the psychological work demands (e.g., workload) were a risk factor. In addition, workers who experienced more psychological distress after the PTE were at greater risk of being (re)-exposed to aggressive behaviour at work two months later. With respect to the third objective, the interviews with the Montréal group who underwent a PTI revealed many negative consequences of PTEs on psychological health, which could be a significant reason for undergoing a PTI. Nevertheless, for some, undergoing a PTI was more preventive. Being encouraged to undergo a PTI by a co-worker (directly or by example) or having previously undergone a PTI were other factors that could motivate making use of a PTI. The participants who underwent a PTI reported a number of benefits in their encounter(s) with a peer helper. Regarding reasons for not undergoing a PTI, participants reported a lack of perceived usefulness, or access to other sources of support (supervisor, co-workers, spouse, psychologist). Other participants did not undergo a PTI because the service was not offered by the supervisor or because they lacked information. With respect to the fourth objective, according to the analysis of the interviews from the three groups, participants expressed the need to be supported by their supervisor and their co-workers. In the weeks and months following the PTE, many workers expressed interest in receiving emotional support from their supervisor and time for dialogue to learn from the PTE. In terms of support from co-workers, in addition to a need for validation and goodwill, the participants mentioned needing concrete support (e.g., to deal with aggressive youth) and information (e.g., to be encouraged to seek help). The participants identified co-workers’ recognition of difficulties as a necessary condition for them to appreciate supportive efforts. Unfortunately, many participants did not receive the support they counted on from their supervisor or co-workers because of a lack of time due to the working conditions. Conclusion: This study confirms that a significant proportion of workers exposed to PTEs experience psychological difficulties. Although support from a supervisor and co-workers can help workers cope with the consequences of a PTE, organizational barriers (e.g., high workload) interfere with this support. In such a context, PTI in its current form must be improved in order to become an effective support measure.