Patton's double-double was his third straight and seventh this season for the Tigers (4-18, 2-8 Southwestern Athletic Conference), who won their first game since beating the Jaguars 61-57 on Jan. 8.
Southern (4-18, 3-7) led by seven early in the second half. The lead went back and forth, with the Jaguars ahead 42-39 with 3:46 to go.
Layups by Steven Dandridge and Derron Hobbs pushed Grambling State ahead 43-42 with 2:40 left.
Southern got to 46-45 with 38 seconds left, then Hobbs hit two free throws and Patton sealed the win by making 1 of 2 foul shots with 1 second left.
Patton shot 3 of 18 from the field, but made 9 of 12 free throws.
Jameel Grace had 12 points for the Jaguars and Frederick Coleman had five blocks.