Background: Mesh is recommended for umbilical hernias with defects > 1 cm to reduce recurrence. For umbilical hernias with defect width ≤ 1 cm, the literature is sparse. The aim of this nationwide cohort study was to assess outcomes after suture and mesh repair of umbilical hernias with defect width ≤ 1 cm and to evaluate outcomes after onlay mesh repair specifically. Methods: By merging data from the Danish Hernia Database and the National Patients Registry from 2007 to 2018, patients undergoing elective open repair of an umbilical hernia with defect width ≤ 1 cm were identified. Available data included details about comorbidity, surgical technique, 90-day readmission, 90-day reoperation and operation for recurrence. Results: A total of 7849 patients were included, of whom 25.7% (2013/7849) underwent mesh repair. Reoperation for recurrence was significantly decreased after mesh repair 3.1% (95% C.I. 2.1–4.1) compared with suture repair 6.7% (95% C.I. 6.0–7.4), P < 0.001. Readmission and reoperation rates were significantly higher for mesh repair 7.9% (159/2013) and 2.6% (52/2013) than for suture repair 6.5% (381/5836) and 1.5% (89/5836), P = 0.036 and P = 0.002, respectively. Onlay mesh repairs had the lowest risk of recurrence 2.0% (95% C.I. 0.6–3.5), and readmission [7.9% (65/826)] and reoperation [3.9% (32/826)] rates within 90 days were comparable to suture repairs [6.5% (381/5836)] and [3.3% (192/5836)], P = 0.149 and P = 0.382, respectively. Conclusions: Even for the smallest umbilical hernias, mesh repair significantly decreased the recurrence rate. Onlay mesh repair was associated with lowest risk of recurrence without increasing early complications.