After Tiziani fired a 65 in the final round to enter the clubhouse in the lead at 8-under-par 280, Sutterfield, who posted a 69, drained a 12-foot putt for a birdie at the last to force the playoff.
The duo returned to the par-five 18th and Sutterfield reached the green in two after a solid approach shot. Tiziani was not as fortunate, as his second shot to the 18th found the hazard to seemingly give Sutterfield the victory.
Sutterfield ran his eagle putt past the hole, but converted for birdie coming back for the win.
'I just can't believe this,' said Sutterfield. 'I have heard other players say it is really hard to describe your first win and right now, I just can't. I always thought I could win out here, but I just didn't know if I believed it, if that makes any sense.'
Sutterfield began the day with a two-shot edge on the Fazio Foothills Course at Barton Creek Resort and tallied a single birdie over his first nine holes.
The 35-year-old added a birdie at the 12th but a bogey at the par-5 15th left him vulnerable to Tiziani's charge.
Sutterfield pulled it together down the stretch with a birdie at the 17th and the clutch birdie putt at the 18th to force the extra session before taking home the title.
Craig Taylor finished alone in third place at 4-under-par 284. Erik Compton and Dan Swanson shared fourth place at 3-under-par 285.
Steve Scott took sixth place at 2-under-par 286 while Jason Allred, Rob McMillan, Kris Mikkelsen and Philip Jonas tied for seventh at even-par 288.