Objective Accumulated evidence suggests that approximately one third of people with a serious mental illness (SMI) experience elevated self‐stigma. Narrative enhancement and cognitive therapy (NECT) is a structured group‐based intervention aimed to reduce self‐stigma. The current study aims to examine the effectiveness of NECT. A quasi‐experimental design. Design Baseline and follow‐up data were collected and outcomes were compared between 63 persons with SMI who participated in NECT and 56 persons who received treatment as usual. Results The NECT treatment group showed significant (p < .05) reductions in self‐stigma and increases in self‐esteem, quality of life, and Hope‐Agency scores between pre‐ and posttreatment assessments, compared with the control group. Conclusions The current results provide preliminary support for the use of NECT as an effective treatment to reduce self‐stigma and its implications for treatment and practice are discussed.