The study examined the effect of human capital investment on return on investment of listed deposit money banks in Nigeria covering 2010-2019 (10 years). The independent variables were proxied by staff cost, number of staff and employee compensation to sales, while the financial performance was proxied by return on investment. Secondary data for this study was extracted from the sampled twelve (12) listed deposit money banks annual financial reports for the period studied. Using the panel regression technique, it was found staff cost, employee compensation to sales and number of staff had insignificant effect on return on investment. It was therefore recommended that banks should institute effective investment plans on various aspects of staff training, retraining, seminars and workshops. Also, management should intensify initiatives, greater understanding and the balance of cost of maintaining the staff in the long run so that employee performance can be improved in the banking sector. Thus, the management should also find initiatives for greater understanding and a balance of cost of maintaining the staff in the sector.