The knowledge and attitude of researchers can affect the validity of laboratory animal (LAN) research. However, studies show that not all researchers possess the required knowledge and appropriate attitude for performing valid research on animals. This may have several reasons, such as high heterogeneity in the educational backgrounds of researchers in animal trials. In this study, we hypothesized that properly designed intensive educational intervention could improve the knowledge and attitude of a mixed population of researchers, regardless of their heterogeneity. We delivered 10 country-wide two-day LAN workshops for academic members, postgraduate students and members of the ethics committees of the medical universities in Iran. Using pre-/post-intervention design, we found that the intervention highly significantly (