The unseeded Sun, who grabbed the attention of the tennis world in July, was beaten in straight sets, 7-6 6-4, to give sixth seed Noskova her first WTA title.
Sun played dazzling tennis throughout the tournament and that was the case again in the final, but her inability to convert break points proved ultimately costly.
Sun, who hails from Te Anau in Southland, started nervously, losing her first service game, but fought back soon after to break Noskova's serve and the players exchanged games in a tight first set.
It went to a tie-breaker and at one stage Sun was two set points up, but couldn't ram home her advantage and Noskova came back to take the set 7-6.
It was the break points that were damaging Sun, as she succeeded with one from six opportunities in the set.
Noskova broke Sun's service early in the second set, and from there the Czech played the steadier tennis, despite some sizzling aces and ground strokes from Sun.
Ranked 57th before the tournament in the WTA rankings, Sun will will rise to 41st in the world when the latest WTA rankings are released on Monday.
She will contest the US Open in New York next week.
"Even though I lost in the final it was still a great, great week," Sun told the crowd at the presentation.
"Gracias, te amo (thanks, I love you) Monterrey."
She beat third seed Ekaterina Alexandrova in the semi-finals.
