The command said the air strikes were conducted on Friday, in coordination with Libya's Government of National Accord, hitting a desert camp 240 kilometers southeast of the city of Sirte.
"The camp was used by ISIS to move fighters in and out of the country; stockpile weapons and equipment; and to plot and conduct attacks", it said in a statement using an alternative acronym for the Islamic State group.
The air strikes were believed to be the first in Libya by US forces since US President Donald Trump took office in January.
The last known US air strikes were carried out in early January under then-president Barack Obama, targeting two IS camps where militants were suspected of actively planning operations in Europe.
The US statement said 17 IS militants were killed and three vehicles were destroyed in Friday's strikes. It provided few other details.
"The United States will track and hunt these terrorists, degrade their capabilities and disrupt their planning and operations by all appropriate, lawful, and proportional means, including precision strikes against their forces, terror training camps and lines of communication, as well as partnering with Libyan forces to deny safe havens for terrorists in Libya", the command said.