
Nyanza region in the Western part of Kenya has the highest concentration of non-governmental organizations (NGOs) implementing HIV and AIDS interventions. Nonetheless, the region is cited to have a high prevalence HIV infection of 15.3% while the prevalence rate for Kenya stands at 7.4%, this has partly been blamed on poorly formulated strategies that have failed to reduce new HIV infections in Nyanza to zero.The purpose of the study was to examine the influence of strategy formulation on performance of HIV and Acquired Immune-Deficiency Syndrome (AIDS) interventions managed by NGOs in Nyanza Region and the moderating influence of stakeholder participation on such relationship. This study used a positivist and interpretive paradigms adopting an ex post facto research survey design. Both quantitative and qualitative approaches. The target population for the study was 18 the departmental heads of program management, 18 monitoring and 18 evaluation and program implementation in NGOs registered by the NGO council as implementing HIV and AIDS interventions as a major focus and operating within Nyanza Region. The study also targeted the directors of the three governing bodies for HIV programming. The population was thus 60 respondents. Non-probability purposive sampling was used to pick the respondents. The research used two instruments: questionnaires, Interviews schedules. Content validity was measured by using the Content Valid Index (CVI). The researcher used Cronbach's Alpha reliability to measure the internal consistency of the questionnaires, r (6 items)=0.839. Data analysis was done through descriptive statistics and inferential statistics such as chi-square odds ratio, hypothesis testing, logit regression modeling. Organisations that did strategy formulation to a small extent were 1.091 more likely to have non-performing HIV/AIDS interventions compared to those that conducted strategy formulation to a large extent, X2(1) =11.018, p= 0.049, CL=95%. Similarly organizations engaging stakeholders in strategy formulation to a small extent were 1.111 more likely to more likely to have non-performing HIV/AIDs interventions compared to those that engaged stakeholders to a large extent, X2(1) =5.030, p= 0.033, CL=95%. There was a significant relationship between strategy formulation and performance of HIV and AIDS interventions managed by non-governmental organisations in Nyanza Region, critical value= 3.84 and the X2(1) value=11.018, 3.84 <11.018.There was a significant moderating influence of stakeholder participation on the relationship between strategy formulation and performance of HIV and AIDS interventions managed by non-governmental organisations in Nyanza Region. Critical value= 3.84 and the X2(1) value =5.030, 3.84 <5.030. The study recommends that the NGOs managing the HIV and AIDS interventions should strengthen their strategy formulation processes and engage stakeholders more meaningfully in the strategy formulation process.