PurposeOn the basis of behavioural agency theory and resource-based view, this study investigates the influence of family firm birth mode (i.e. indirect-established or direct-established), family entering time on R&D investment and the moderating role of the family entering time on the relationship between birth mode and R&D investment.Design/methodology/approachThe authors collected 2,990 firm-year observations from family firms listed on A-share in China from 2008 to 2016 in the China Stock Market and Accounting Research database. They used pooled regression for data analysis and Tobit regression for robustness checks.FindingsIndirect-established family firms show more inclined behaviour towards R&D investment than direct-established counterparts. Family entering time positively affects the R&D investment of family firms. Moreover, family entering time plays a significant moderating role in the relationship between family firm birth mode (i.e. indirect-established or direct-established) and R&D investment.Originality/valueTo the best of the authors’ knowledge, this work is a pioneering study that introduced the concept of family firm birth mode (i.e. indirect-established or direct-established) and family entering time. This work is novel because it differentiated family firms according to their birth modes, an approach which is a contribution to the existing literature of family firms. Moreover, the investigation of the moderating role of family entering time has also produced notable results that help understand the impact of family entering time on different types of family firms. The interpretation of outcomes according to behavioural agency theory also produced useful insights for future researchers as well as for policymakers.