Human Immunodeficiency Virus (HIV) and acquired immunodeficiency syndrome (AIDS) are diseases that still pose a threat to all parts of the world, particularly in less economically developed regions. However, it continues to be a problem in many high-income countries. The epidemiological picture in Spain offers an interesting case study for analysis to answer whether local interventions to confront HIV transmission, morbidity, and mortality are more effective than solely national or international efforts to reduce the effects of the disease. In this thesis, I rely on qualitative data in the form of key informant interviews and field notes collected in Barcelona, Spain, to demonstrate the significant role that grassroots organizations play in combating HIV in the Spanish context. CheckPoint Barcelona and ACATHI are two organizations in Barcelona, Spain that seek to improve such outcomes by directly providing support for communities at risk of poor outcomes after a late diagnosis of HIV and of contracting HIV in general. I find that local, non-governmental organizations are the driving force in combating HIV in Spain through three approaches: biomedical interventions, education and prevention initiatives, and social support for affected communities. Collectively, these findings suggest that non-governmental organizations, like ACATHI and CheckPoint should be supported to continue achieving desired HIV objectives.