Seattle (7-13, 2-8 WAC) trailed 22-20 at halftime but started the second half on a 21-9 run capped off by Obasi's lay-up with 7:41 remaining in the game to give the Redhawks a 41-31 lead and didn't look back.
Louis Green scored 13 points, grabbed seven rebounds and had four blocked shots for Seattle while teammate Jarell Flora chipped in with 11.
The Redhawks shot only 38.6 percent from the field and were a dismal 1 of 15 from beyond the arc. The two teams combined to go 2 for 24 from 3-point land.
Chris Cunningham led San Jose State (9-12, 3-7) with 12 points including an 8 for 10 effort from the free-throw line and grabbed 11 rebounds. D.J. Brown chipped in with 10 points, five rebounds and two assists.