Monaco, the No. 3 seed in Dusseldorf, finished off all four of his break chances -- two in each set -- in collecting the eighth title of his ATP career. He's won five of his last six finals appearances, a string dating from February 2012.
Monaco edged ahead with a break in the ninth game of the first set and served out for the lead. He established an early advantage in the second set and finished the championship match with a break.
Even with losing his serve once in the first set, Monaco won 72 percent of the points on serve. He dropped only six points on serve in the tournament's final set.
Nieminen, who was seeded sixth this week, falls to 2-11 in title matches.
The champion's check of more than $95,000 lifts Monaco, a pro since 2002, past the $6 million mark in career winnings. Nieminen took home about $50,000 as the runner-up.
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