Objectives Evidence comparing the economic and patient values of the World Health Organization’s preferred (dolutegravir 50 mg [DTG]-based) and alternative (low-dose [400 mg] efavirenz [EFV400]-based) first-line antiretroviral regimens is limited. We compared patient-reported outcomes (PROs), costs, and the cost-utility of DTG- versus EFV400-based regimens in treatment-naive HIV-1 adults in the randomised NAMSAL ANRS 12313 trial in Yaoundé, Cameroon. Methods We used clinical data, PROs, and health resource use data collected in the trial’s first 96 weeks (2016–2019). Quality-adjusted life-years (QALYs) were computed using utility scores obtained from the 12-item Short Form (SF-12) generic health scale. Other PROs included perceived symptoms, depression, anxiety, and stress. In the 96-week base-case analysis, we estimated the unadjusted and multivariate-adjusted (1) mean costs (in US$, 2016 values) and QALYs/patient, (2) incremental costs and QALYs/patient, and (3) net health benefit (NHB). Outcomes were extrapolated over 5 and 10 years. Uncertainty was assessed using the cost-effectiveness acceptability curve and scenario and cost-effective price threshold analyses. Results In the base-case analysis, the NHB (95% confidence interval) for the DTG-based regimen relative to the EFV400-based regimen was 0.056 (− 0.037 to 0.153), corresponding to an 88% probability of DTG being cost-effective. A 10% decrease in this regimen’s price (from $5.2 to $4.7/month) would increase its cost-effectiveness probability to 95%. When extrapolating outcomes over 5 and 10 years, the DTG-based regimen had a 100% probability of being cost-effective for a large range of cost-effectiveness thresholds. Conclusions At 2020 antiretroviral drug prices, a DTG-based first-line regimen should be preferred over an EFV400-based regimen in sub-Saharan Africa. Trial Registration ClinicalTrials.gov Identifier: NCT02777229. Supplementary Information The online version contains supplementary material available at 10.1007/s40273-020-00987-3.