This paper empirically examines the mediating role of innovativeness on the relationship between technological capability and sustainability performance of medium and large manufacturing firms in Nairobi County, Kenya. The study surveyed 302 firms and applied Hayes’ PROCESS macro (Model 4) to test the direct effect of technological capability on sustainability performance and the indirect (mediated) effect of innovativeness, using bootstrap confidence intervals for inference. Technological capability has a significant and positive total effect on sustainability performance. Controlling for innovativeness, the direct effect remains positive and significant and the indirect effect via innovativeness is significant indicating complementary (partial) mediation. Technological capability positively predicts innovativeness and innovativeness positively predicts sustainability performance. This research recommends that firms should pair investments in technological capability with organizational processes that systematically translate those capabilities into innovation such as cross-functional R&D routines, eco-innovation programs, and learning systems and monitor innovation and sustainability KPIs to ensure technological assets are effectively leveraged.