This study examined the relationship between firm capabilities, innovations and growth of firms in the sanitation subsector among firms in Kampala city and Wakiso district. The objectives were to examine; relationship between firm capabilities and innovation; innovation and growth of firms; firm capabilities and growth of firms; and test the influence of innovation on the relationship between firm capabilities and growth of firms. This was a cross-sectional research design based on a qualitative approach. Data was obtained from owners of 12 firms within the sanitation subsector using a structured interview guide. Validity of the interview was obtained by ensuring credibility, conformability and transferability and reliability through audit trail, maintaining and preserving all transcripts and notes for the study. Atlas. it (v.7) was used to analyze data to identify important narratives upon which interpretation was based. This study ascertained that firm capabilities influence innovation among firms. The study found that management capabilities were critical in determining the level of innovation within firms. Funding capabilities was also revealed as important in determining innovation. It was obtained that operational capability can determine the level of innovation. This study further ascertained that growth of firms is inclined to the level of innovation. The study found that new processes and new products facilitate firms to growth. Firm capabilities were found to determine growth of firms. Management capabilities, funding and operational capabilities were all relevant in determining growth of firms. The study established that innovation influences the relationship between firm capabilities and growth of firms. This study recommends; boosting management capabilities; increased innovation; and enhancement of operation capability.