During the past decade, Jordan has undertaken substantial reforms aiming at restructuring its stock market in order to strengthen its role in promoting investment and allocating capital efficiently. This paper empirically investigates the impact of stock market development on capital investment at the firm level by assessing the investment-q sensitivity. In addition, this paper examines the impact of concentrated ownership, a salient institutional feature of listed Jordanian companies, on the investment-q sensitivity. The findings of this study indicate that investments by Jordanian firms respond significantly and positively to market signals. Furthermore, the results show that a company responds more efficiently to market signals as ownership concentration increases, which suggests that large ownership stakes align the interests of large shareholders with those of the firm.