It was the first win at UMES for coach Bobby Collins.
Byron Ashe led Mount St. Mary's with nine points and Junior Robinson added eight. The Mountaineers were held to 29.8 percent shooting (14 of 47) and were outrebounded 38-26.
UMES led 26-11 at halftime, but Mount St. Mary's opened the second half on an 8-2 run to pull within 28-19. Walker responded by scoring his teams' next 10 points for a 36-25 lead.