WASHINGTON—Citing national security, lawmakers are looking to ban military purchases of Chinese-made drones—which could boost prospects for U.S. makers struggling to compete.

The National Defense Authorization Act passed by the Senate last week would bar Chinese drones for military use as U.S. officials grow worried that the country’s reliance on Chinese drones may be putting critical U.S. infrastructure at risk. They are concerned the drones may be sending information back to the Chinese government or hackers elsewhere to...