The testing at the White Sands Missile Range in New Mexico included mid- and long-range firings against simulated targets in preparation for an initial operational test and evaluation exercise, which are expected later this year.
Lockheed said the tests, with military personnel operating the Guided Multiple Launch Rocket System's fire control equipment, proved successful but additional details were not provided.
The Alternative Warhead, being developed by Lockheed-Martin sub-contractor ATK, is a cluster bomb sub-munition with a diminished danger of unexploded ordnance.
Lockheed received a three-year $79 million award to develop the warhead in 2012.
"The AWP is part of a U.S. Department of Defense plan to create a GMLRS variant which meets the DOD's cluster-munition policy," the company said. "The Lockheed Martin GMLRS AWP will also be compliant with the provisions of the (UN) Convention on Cluster Munitions international treaty."