Abstract: To meet new Department of Defense (DoD) energy standards, buildings are being constructed, and existing buildings are being retrofitted with tighter envelops. These new standards can reduce operational costs significantly but also limit fresh outdoor air coming into the built environments. This can result in the accumulation of harmful substances within buildings, which can have adverse effects on its occupants. New photocatalytic coatings may be a solution to this ever-increasing problem as they have the ability to destroy both chemical and biological toxins when activated with light. This work evaluated a novel indoor-light-reactive photocatalytic coating for its ability to eliminate or reduce microbial contamination under in situ test conditions. However, air and surface sampling revealed no reduction in either viable fungi and bacteria or total air-borne mold spores. Additionally, no significant differentiation could be made in the composition of volatile organics between the treated and untreated areas. However, testing the photocatalytic activity of the coating with standardized test methods and increased illumination, revealed the coating did exhibit antimicrobial activity against mold, bacteria, and viruses. This suggested that there may be limited benefit to using the indoor-light-reactive photocatalytic coating to inhibit microbial contamination unless specific lighting conditions can be met.