Purpose: The purpose of this paper is to conduct a critical review of the mediation studies published in the field of Human Resource Development (HRD) to discern if the study designs, the nature of data collection and the choice of statistical methods justify the causal claims made in those studies. Design/methodology/approach: This paper conducts a critical review of published refereed articles that examined mediation in Human Resource Development Quarterly, Human Resource Development International, Advances in Developing Human Resources and European Journal of Training and Development. Mediation studies published in these journals from 2000 to 2015 were identified and coded. The four journals sampled were chosen to provide breadth of coverage of the different types of empirical studies published in the field of HRD. Findings: The review findings imply that HRD scholars are not employing experimental or longitudinal designs in their studies when randomized experiments and longitudinal studies with at least three waves of data collection are regarded as the golden standards of causal research. Further, the findings indicate that sophisticated statistical modeling approaches like structural equation modeling are widely used to examine mediation in cross-sectional studies and most importantly, a large number of such studies do not acknowledge that cross-sectional data does not allow definite causal claims. Research limitations/implications: Although the findings urge us to rethink the inferences of mediation effects reported over the past 15 years in the field of HRD, this study also serves as a guide in thinking about framing and testing causal mediation models in future HRD research and even argues for a paradigm shift from a positivist orientation to critical and postmodern perspectives that can accommodate mixed methods designs for mediation research in HRD. Originality/value: This paper presents a critical review of the trends in examining mediation models in the HRD discipline, suggests best practices for researchers examining the causal process of mediation and directs readers to recent methodological articles that have discussed causal issues in mediation studies.