Abstract: The aim of this article is to determine the impact of in-house training (defined as any training provided by firms in the workplace) on employee productivity, employee remuneration and net employee productivity gains when diversity attributes of the workplace are taken into consideration. The manufacturing industry of Gauteng Province of South Africa is used as a case study. Fixed-effect panel data estimations were performed in order to determine the diversity-based employee productivity, remuneration and net productivity differentials of in-house training. The results accentuate the important positive productivity, remuneration and net productivity spill-over effects created by in-house training opportunities. The outcomes of the study also confirm the importance of a workplace that is more gender diverse, racial diverse and in which skilled and older experienced employees are retained if the productivity spill-over effects generated by in-house training opportunities are to be enhanced.