Aim: Bascom's cleft-lift procedure for pilonidal sinus disease under tumescent local analgesia is feasible and well tolerated with favourable short-term outcomes. We aimed to assess the 10-year treatment success rate after cleft-lift under tumescent local analgesia. Method: This was a single-centre cohort study based on prospectively registered perioperative data and survey data with additional data from electronic medical records. The cleft-lift procedure was performed under tumescent local analgesia in a day-surgical setting at a tertiary referral hospital between 1 July 2008 and 31 March 2014. The primary outcome was the 10-year risk treatment success defined as complete wound healing within 180 days of surgery or no recurrence assessed with competing risk analyses. Secondary outcomes were time to complete wound healing, persistent pain and cosmetic satisfaction. Results: Two hundred patients with complex pilonidal sinus disease were included. Indication was incomplete wound healing after pilonidal sinus surgery in 43 (21.5%) patients, recurrence after previous intervention in 78 (39.0%) or moderate to complex sinuses assessed by a consultant surgeon in 79 (39.5%). One hundred and ninety-five patients had complete wound healing within 180 days with a median time of 29 days (interquartile range 16–47). The cumulative risk of 10-year recurrence was 11.3% (95% CI 6.2%–16.4%) with a median follow-up time of 8.5 (1.0–10.7) years. Treatment success was 86.1% (95% CI 80.6%–91.5%). No significant predictors were associated with recurrence, and 90% of patients experienced no persistent pain. Conclusion: Cleft-lift performed under tumescent local analgesia has an acceptable 10-year treatment failure rate, making the method feasible in a day-surgery setting.