This study examined the relationship between human capital investment and productivity of pharmaceutical firms in Nigeria. The study specifically examined the relationship of: staff education/training, pension contributions, staff salaries and wages to cost of sales of pharmaceutical firms in Nigeria. Data of the study were sourced from annual reports of the five (5) sampled pharmaceutical firms. Hypotheses raised were analysed using Correlation Coefficient, result of the hypotheses shows that staff training expenses of pharmaceutical firms in Nigeria positively and significantly relate with the firms cost of sales with Pearson Correlation result of .723** and P value of 0.000. This implies that staff training cost has a positive influence on the return on investment of the selected firms under study. It was discovered from the study that pension contributions of pharmaceutical firms in Nigeria positively and significantly relate with the firms return on investment with Pearson Correlation result of .567** and P value of 0.000. This implies that pension contributions have a positive influence on cost of sales of pharmaceutical firms in Nigeria. Finally, the findings showed that staff salaries and wages of pharmaceutical firms in Nigeria positively and significantly relate with the firms cost of sales with Pears on Correlation result of .665** and P value of 0.000. This implies that Staff salaries and wages does significantly relate with cost of sales of pharmaceutical firms in Nigeria. Based on the findings, the study recommends among others that firms should implement more of on-the-job training in order to reduce expenses on staff training. On the job training should be augmented with other forms of staff training.