This article analyses the level of secondary traumatic stress in Portuguese social workers. Social workers practice their profession in conditions that generate stress and trauma on a daily basis; this is triggered by clients’ anxiety, threats to the integrity of the professionals, and situations that have a negative impact on professional practice. This study was conducted in organisations registered under the Social Charter, which coordinates institutions of social policies operationalised in Portugal. A Secondary Traumatic Stress (STS) index was used to obtain data regarding practitioners’ practice for the characterisation and identification of situations of trauma experienced by clients, and their impact on social workers. Questionnaires were sent to the organisations via email, and in return 872 were answered by social workers. The results reveal a score of 2.65 on the Secondary Traumatic Stress Scale, and this appears more apparent in the Arousal dimension, followed by Avoidance and lastly Intrusion. Furthermore, it is evident that the conditions of professional practice and the sector in which professionals work generate STS because they significantly expose social workers to the traumas of the most vulnerable clients. The professionals recognise these incidences, which feasibly denotes that there is a possibility to avoid and act against STS by stimulating professionals’ internal resilience and psychological capital, increasing professionals’ access to professional supervision and improving working conditions in the organisations where they practice.