Although current quality indicators of colonoscopy recommend 6 minutes as the minimum standard for withdrawal time (WT), the impact of a WT longer than 6 minutes on neoplasia detection is unclear.A multicenter randomized controlled trial involving 1027 patients was conducted from January 2018 to July 2019. Participants were randomly divided into a 9-minute (n=514) and 6-minute (n=513) WT group, and a timer was used to adjust the withdrawal speed. The primary outcome was the adenoma detection rate (ADR).Intention-to-treat analysis showed a significantly higher ADR in the 9-minute versus 6-minute WT group (36.6% vs. 27.1%, P=0.001). Prolonging WT from 6 to 9 minutes significantly increased ADR of the proximal colon (21.4% vs. 11.9%, P<0.001) as well as of the less experienced colonoscopists (36.8% vs. 23.5%, P=0.001). Improvements were also observed in the polyp detection rate (58.0% vs. 47.8%, P<0.001), and mean number of polyps and adenomas detected per colonoscopy (1.1 vs. 0.9, P=0.002; 0.5 vs. 0.4, P=0.008, respectively). The higher ADRs in 9-minute WT were also confirmed by the per-protocol (PP) analysis and subgroup analyses, with an increased rate of sessile serrated lesion detection in the 9-minute WT by PP analysis (4.0% vs. 1.3%, P=0.04). Multivariate logistic regression demonstrated that the 9-minute WT was independently associated with increased ADR (P=0.005).Prolonging WT from 6 to 9 minutes significantly improved ADR, especially in the proximal colon and for less experienced colonoscopists. A 9-minute WT benchmark should be considered as one of the quality indicators of colonoscopy.