Jensen completed 15 of 20 passes for 268 yards to lead Montesano (12-2) to its first title since 1994. He threw a 42-yard touchdown pass to Richard Smith on the final play of the first half to put Montesano up 22-21 after Royal led 21-10 early in the second quarter.
Mendenhall rushed for 172 yards on 13 carries, including scoring runs of 41 and 82 yards. Ibabao added 84 yards on 11 carries.
Alex Myrick completed 9 of 15 passes for 102 yards and three touchdowns to lead Royal (13-1), which was seeking its sixth state title and first since 2007. Myrick also rushed for 109 yards on 28 carries. Damien Dela Rosa rushed for 158 yards and one touchdown on 17 carries.