Safin, playing with the same crushing authority that had seen off Andre Agassi in the semi-finals, emerged from a run of three broken service games with a 3-1 lead on his way to taking the first set in just 29 minutes.
Nalbandian made two tired mistakes to hand Safin the second set in game 10 and the Russian cruised through the third to complete victory in one hour 52 minutes.
"The match was quite a lot easier than I'd expected," said the third-seeded Safin. "I don't think I can go on playing like this forever -- it's too good."
Victory was enough to take Safin into sixth place in the Champions Race, ahead of Tim Henman, and closer to a spot in next month's season-ending Masters Cup in Houston.
Nalbandian, beaten in four of five previous meetings with Safin, was always going to have to be at his peak to unsettle the Russian.
As a result, the Argentine went for his shots from the start but he was unable to match Safin's combination of power and accuracy.
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"I had many chances to be more aggressive and win more points but I didn't take advantage as I would have liked."
Nalbandian recovered from his first-set mauling to edge ahead in the second when Safin saved one break-point with an ace only to drop an approach short on the second and give the Argentine an easy passing chance.
Nalbandian lost that advantage in the sixth game, when he wafted a tired backhand into the net on the first of two break-points, and from that moment on Safin never let go.
The Russian took the second set thanks to two unforced errors from his opponent and got the crucial break at the start of the third when Nalbandian overhit yet another forehand.