The two nations have been working together since 2006 to develop a variant of the Standard Missile-3, a ship-launched missile that operates as part of the Aegis Ballistic Missile Defense System.
Friday's test off Kauai in Hawaii saw the Standard Missile-3 "Block IIA" successfully hit its target in space, the US Missile Defense Agency said.
According to the MDA, America has so far spent about USD 2.2 billion on the system and Japan about USD 1 billion.
"It makes sense for the US and Japan to share some of that burden."
More From This Section
Mitsubishi and Raytheon both make parts of the missiles, which are assembled in the United States, and which are designed to defeat medium- and intermediate-range missiles.
The test occurred as Pentagon chief Jim Mattis was in East Asia on his first overseas trip as defense secretary.
He said Friday that any nuclear attack by North Korea would trigger an "effective and overwhelming" response, as he sought to reassure Asian allies rattled by President Donald Trump's isolationist rhetoric.