Background and Aim: Colonoscopy can be performed with two-operator (2OP) or one-operator (1OP) methods. This study aimed to investigate the feasibility and colonoscopy quality outcomes for the two different colonoscopy insertion techniques. Methods: One colonoscopist from Changhua Christian Hospital learned and changed the colonoscopy insertion technique from 2OP to 1OP during 2013. Real-life results of screening colonoscopies performed by this colonoscopist between these two insertion techniques (year 2012: 2OP vs year 2014: 1OP) were retrospectively reviewed and compared. Results: In total, 219 screening colonoscopies were reviewed (2OP group, n =103 vs 1OP group, n =116). No differences were noted between both groups in terms of patient age, gender, weight, and height. The overall cecum intubation was 98.2%, adenoma detection rate (ADR) was 29.7%, and colonoscopy withdrawal time was 518.58 972.04s. On comparing colonoscopy quality outcomes between both methods, no differences were observed in cecal intubation rates (2OP vs 1OP: 100 vs 96.6%, P = 0.1626), ADR (28 vs 31%, P = 0.7401), and colonoscopy withdrawal time (454.88 +/- 178.21 vs 576.92 +/- 1325.01s, P = 0.355). However, the 1OP group demonstrated significantly shorter colonoscopy insertion time (2OP vs 1OP: 298.28 +/- 202.95 vs 216.21 +/- 121.99s, P = 0.003). Conclusion: Colonoscopy quality outcomes were not impaired when one endoscopist changed the colonoscopy practice pattern from 2OP to 1OP. However, 1OP significantly shortened the colonoscopy insertion time.