The objectives of this systematic review were to investigate the effectiveness of male-only weight loss and weight loss maintenance interventions and to identify intervention characteristics associated with effectiveness. In May 2011, a systematic literature search with no date restrictions was conducted across eight databases. Twenty-four articles describing 23 studies met the eligibility criteria. All studies included a weight loss intervention and four studies included an additional weight loss maintenance intervention. Study quality was mostly poor for weight loss studies (median = 3/10, range = 1–9) and weight loss maintenance studies (median = 3.5/10, range = 1–6). Twenty-three of 31 individual weight loss interventions (74%) from the eligible studies were considered effective. Meta-analysis revealed a significant difference in weight change favouring weight loss interventions over no-intervention controls at the last reported assessment (weighted mean difference −5.66 kg [−6.35, −4.97], Z = 16.04 [P < 0.00001]). Characteristics common to effectiveness were younger sample (mean age ≤42.8 years), increased frequency of contact (>2.7 contacts/month), group face-to-face contact and inclusion of a prescribed energy restriction. Preliminary evidence suggests men-only weight loss programmes may effectively engage and assist men with weight loss. However, more high-quality studies are urgently needed to improve the evidence base, particularly for maintenance studies.