We analyse the impact of public subsidies on private sector research and development (R&D) activity for a sample of East German firms. Using propensity score matching, our empirical results indicate that subsidized firms indeed show a higher level of R&D intensity (R&D expenditures relative to total turnover) and a higher probability for patent application compared with non‐subsidized firms. We find that, on average, the R&D intensity increases from 1.5% to 3.9%. The probability of patent application rises from 20% to 40%. These results closely match earlier empirical findings for East Germany. Given the fact that the East German innovation system is particularly driven by small‐ and medium‐sized enterprises (SMEs), we draw special attention to the effectiveness of R&D subsidies for this latter subgroup. Here, no specific empirical evidence is available so far. Our findings indicate that policy effectiveness also holds for private R&D activity of SMEs, with the highest increase in terms of R&D intensity being estimated for microbusinesses with up to ten employees.