We exploit quasi-exogenous variation in passive ownership around the Russell 1000/2000 cutoff to explore the causal effects of passive ownership on the securities lending market. We find that passive ownership causes an increase in lendable supply and short interest, while lending fees remain largely unchanged. The utilization ratio—i.e., the ratio of short interest over lendable supply—goes up, implying that shorting demand increases more than lendable supply. We argue that this additional demand results from an increase in the quality of lendable supply as passive funds are less likely to recall stock loans. Finally, we document that passive ownership-induced short selling improves information efficiency around negative earnings news.