We examine the effect of intellectual capital on firms' innovativeness and the moderating role of firm size in software development firms in Kenya. Using moderated regression analysis, we found support for the proposition that human and social capital enhance firms' innovativeness. We did not, however, find any significant effect of organizational capital on firms' innovativeness. The results from the moderated regression suggest that the smaller the firm, the stronger the influence of intellectual capital on firms' innovativeness. The results therefore indicate that human and social capital are critical in the innovation process and so firms that neglect these capitals are unlikely to realize the potential to innovate particularly in software development firms.