Larry Nance Jr. added 11 points and 12 rebounds for Wyoming (15-2, 2-2 MWC), which used a tough defense to hold the Aztecs to just nine first-half points.
Derrious Gilmore also reached double figures with 13 points for the Cowboys.
Jamaal Franklin led San Diego State (14-4, 2-2) with 13 points, but committed five turnovers.
Winston Shepard provided 10 points for the Aztecs, who suffered a second straight loss for the first time this season.
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