Trauma-focused guided self-help (TF-GSH) is an important alternative to psychological therapy delivered by a therapist. This meta-analysis evaluates the efficacy of TF-GSH in reducing posttraumatic stress disorder (PTSD) symptoms and comorbid depressive and anxiety symptoms. A total of 17 trials were included that compared a TF-GSH intervention (N = 610) to various control comparators (N = 570). Control conditions included treatment as usual (k = 2), waiting list (k = 11), phone monitoring (k = 1), nontrauma writing (k = 1), general support (k = 1), and supportive counseling (k = 1). A moderate- to large-sized effect favouring TF-GSH was observed for PTSD (k = 17, g = −0.81, 95% confidence interval [CI]: −1.24, −0.39) and a moderate-sized effect was observed for depressive (k = 13, g = −0.73, 95% CI: −1.16, −0.31) and anxiety (k = 11, g = −0.72, 95% CI: −1.18, −0.27) symptoms, with considerable heterogeneity. Moderator analyses were all not statistically significant. Results indicate that TF-GSH is a promising treatment for PTSD and comorbid depressive and anxiety symptoms. We discuss the nature, extent, and quality of the literature to provide a point of departure for future research. TF-GSH (and unguided self-help) may not be appropriate for certain individuals at certain times. Exploring a broad range of treatment delivery modalities will move the field closer towards a model of evidence-based care in which the likely appropriate dose and type of intervention can be matched to individuals based on presenting problems and other variables.