The World Health Organization is promoting community-based services to end HIV/AIDS by 2030. In Nigeria, studies on community pharmacists' involvement in HIV testing services (HTS) and antiretroviral (ARV) medication therapy management (MTM) are scarce, and no study had evaluated the clients' opinion on community pharmacy HTS. We assessed the community pharmacists' involvement in HIV/AIDS services and clients' opinions of community pharmacy HTS. Semi-structured questionnaires on a five-point Likert scale were administered to 701 selected community pharmacists and 5840 clients in southwest Nigeria in 2019. Data were analyzed with descriptive and inferential statistics. Response rates were 68.6% and 69.8% for community pharmacists and clients, respectively. Only 18.5% of community pharmacists offered rapid HTS and 30% refills of ARV. The total score of their involvement on the HTS was 20.94 ± 17.521 (range 8-40; midpoint 24) and on ARV/MTM was 22.98 ± 19.61 (range 9-45; midpoint 27), while 91% were willing to participate in training. Barriers to integrating services into practice were lack of clinical tools (46.8%), lack of collaboration with other healthcare professionals (39.1%), and lack of training on HIV/AIDS services (36.2%) among others. Also, 77% of the clients were willing to participate in community pharmacy HTS, and about 83% of them responded that knowing their HIV status will help them to take necessary precautionary actions. Community pharmacists' involvement in HIV/AIDS services was low. However, they showed willingness to participate in training to improve services. Also, clients were willing to receive community pharmacies HTS to know their status.