In an all-Spanish affair, Verdasco was comfortable in the first set before he was forced into saving five set points in the second on his way to victory in Houston.
Almagro was well rested after semi-final opponent Sam Querrey withdrew from Saturday's last-four clash with a pinched nerve in his back, but Verdasco, who saw off Santiago Giraldo in his semi-final, made light of Almagro's extra day's rest.
For the fourth seed, victory ended a run of six consecutive defeats in ATP tour finals while Almagro's own losing streak in finals was extended to four.
Verdasco wasted two break points in Almagro's first service game, but broke in his next to take the advantage in the first set.
It was one that he never relinquished, although he did have to save a break point in the ninth game before sealing the opener.
He then wasted another four break points in the third game of the second set, before Almagro broke him for the first time in the very next game.
Verdasco responded in kind in the seventh, before an epic 10th game in which he had to save set points on five occasions on his own serve.
After forcing a tie-break, the world number 29 fell 4-3 behind before reeling off four consecutive points to seal the sixth ATP tour victory of his career.