Background: Community-based test and start (TAS) models have shown the potential to improve clinical outcomes for key populations because early access to treatment will have population level impact by reducing transmission through the promotion and provision of hassle-free quality HIV testing, on the spot ART initiation and unrestricted access to culturally competent health professionals. We assessed the effectiveness of a pioneer community-based test and start (TAS) model for key populations in Lagos along UNAIDS 90/90/90 cascade. Methods: Men who have sex with men (MSM), female sex workers (FSW), and persons who inject drugs (PWID), >14 years of age were recruited through peer-referral for HIV testing services (HTS) at a community-based KP-friendly clinic in Lagos between June 2015 and September 2016. The clinic provides comprehensive HIV services, including HIV treatment. Those who test positive are enrolled and provided with TAS services. Using routine service data, we deployed descriptive cross tabulations at p < 5% to determine the performance along the 90/90/90 cascade. Results: In total, 8812 KPs comprising MSM (51.6%), FSW (32.7%) and PWID (15.7%) were tested during this period. About one-half (46.4%) were young KP (15-25 years). The majority (76.1%) were male, single (86.1%), almost all (99%) had at least primary school level education, and about one-quarter (25.1%) were employed. Among MSM, 506 (11.1%) tested positive, 276 (54.5%) were initiated on ART, of whom 155 conducted viral load testing and 88 (56.7%) had achieved viral suppression (<1000 copies per milliliter). Among FSW, 88 (3.1%) tested positive, only 28 (31.8%) were initiated on ART, of whom 15 conducted viral load testing and 9 (60%) achieved viral suppression. Among PWID, of 15 (1.1%) who tested positive, only 2 (13%) were initiated on ART