The effectiveness of positive psychology interventions in the treatment of stress‐related difficulties have not been well established. To estimate the effectiveness of positive psychology interventions on the reduction of stress‐related symptoms, a systematic review using PubMed, Scopus, Wiley, Psychinfo, Cochrane and Sage databases with no limitation of date of publication was conducted. We identified additional studies by searching positive psychology reviews and academic books. Only studies trying positive interventions that included measures of anxiety, stress, or posttraumatic stress disorder symptoms were reviewed. We extracted data using predefined data fields and study quality was assessed with the National Institutes of Health study quality assessment tools. Twenty‐nine records were included in this study: 23 controlled trials and six pre‐post studies. Every study showed significant improvement in at least one dimension. Several studies reported improvements in well‐being as well. This review shows promising results of positive psychology interventions as a treatment for stress‐related difficulties. However, important methodological biases and strong heterogeneity among the studies highlight the need for replication and better validation of positive psychology interventions.