Effective innovation policymaking critically relies on monitoring innovation. An emerging literature suggests that trademarks could help measure a larger share of innovations than when only utilizing patents, particularly for small- and medium-sized enterprises (SMEs). This study establishes when trademarks improve the measurement of innovation compared to solely relying on patents as innovation metrics, by examining the propensity to use trademarks for non-patented innovations from SMEs. We collected multiple original samples of innovations from Dutch SMEs and assessed the extent to which trademarks and/or patents were filed for those innovations. Our results show that trademarks can improve innovation measurement for SMEs, particularly in scale-intensive and supplier-dominated industries and in some service industries—areas where patent propensities are low. Our results bear implications for monitoring innovation and evaluating science, research, and innovation policy. Overall, by combining trademark and patent data, the number of measured innovations by SMEs increases approximately by a relative of 51.8 per cent.