Objectives To evaluate the success rates of dental procedures, the recurrence rates of caries and changes in oral health-related quality of life (OHRQoL) in children following treatment for early childhood caries (ECC) under dental general anaesthesia (DGA) in Chongqing, China. Design A single-centre prospective cohort study conducted from December 2016 to June 2017. Setting A tertiary stomatological hospital in Chongqing, China. Participants A total of 159 children aged 2–5 years who received treatment for ECC under DGA were included. Main outcome measures The primary outcomes were the success rates of dental procedures (the number of successful procedures divided by the total number of procedures) and the recurrence rates of caries. The success and recurrence rates were evaluated by a specialised examiner. The secondary outcome was the change in children’s OHRQoL after DGA treatment, which was measured with the Early Childhood Oral Health Impact Scale (ECOHIS). Results Overall, 117 children (73.6%) and 101 children (63.5%) participated in 6-month and 12-month clinical examinations, respectively, and 151 children (95.0%) completed OHRQoL surveys pretreatment and at 1, 3, 6 and 12 months post-treatment. The resin composite, stainless steel crown, indirect pulp capping, pulpectomy, space maintenance and dental sealant success rates were 89.6%, 96.3%, 96.0%, 94.4%, 76.9% and 92.9%, respectively, at 6 months and 78.8%, 95.1%, 92.2%, 88.9%, 63.6% and 89.3%, respectively, at 12 months. 10 (8.5%) and 19 children (18.8%) developed recurrent caries within 6 and 12 months, respectively. Within 1 year of treatment, the total ECOHIS scores at each post-treatment time point were still significantly lower than those at pretreatment, although they had increased slowly over time. Conclusions Overall, high success rates were obtained for the dental procedures, and the children’s OHRQoL significantly improved after treatment. However, there was a tendency towards caries relapse, and the children’s OHRQoL deteriorated over time.