Chief Petty Officer Jason Finan was the fourth member of the US military to be killed in Iraq by the Islamic State jihadist group, which overran large parts of the country, including Mosul, in June 2014.
Finan died on Thursday "from wounds sustained during an improvised explosive device blast near Bashiqa," the coalition said in a statement, referring to an area northeast of Mosul.
He was advising Iraqi Kurdish forces "when the element he was with came under small arms fire. Finan was repositioning to a more advantageous position when his vehicle struck an improvised explosive device," it said.
"His sacrifice will not be in vain," Lieutenant General Stephen Townsend, the commander of the international anti-IS operation, said in the statement.
"Our troops are in harm's way supporting our partners in their fight against (IS), which presents a very real danger to not only the region, but the United States and our friends and allies around the world as well," Townsend said.
US President Barack Obama repeatedly pledged that there would be no "boots on the ground" to fight IS, but Finan is the fourth member of the US military to be killed in combat in Iraq during the war against the jihadist group.
A US Navy SEAL was killed in northern Iraq in May, while a Marine was killed by rocket fire in March and a special forces soldier died of wounds received during a raid last October.
More than 7,000 coalition military personnel are deployed in Iraq, most of them in advisory or support roles, but special forces have fought IS on the ground, and artillery units are also targeting the jihadists.