It was the world No.5's third consecutive Auckland title and fourth overall, equalling the record of Australian great Roy Emerson.
Ferrer won the match on Saturday in one hour 18 minutes but did not have everything his own way, having to come back from two breaks and set point down in the opening set.
Kohlschreiber didn't lose a point in his first three service games and broke Ferrer in the third game, but he couldn't maintain the standard.
Ferrer was able to break back in the eighth game with some great returns, and though Kohlschreiber broke back immediately, the German failed to convert a set point on his serve and was broken after a series of errors.
Kohlschreiber paid for his mistakes in the tiebreak, going down a mini-break early, and Ferrer closed it out 7-5 without losing a point on his serve.
The disappointment seemed to affect Kohlschreiber as his standard slipped in the second set. A double fault gave Ferrer a break in the fourth game, and another break in the sixth game put Ferrer well on track.
The Spaniard won the match after Kohlschreiber skied a shot high into the stands on Ferrer's first match point.
Earlier, Colin Fleming of Scotland dedicated his doubles victory to his cancer-stricken former partner Ross Hutchins after winning the title in Auckland.
Fleming and Bruno Soares of Brazil, a first-time pairing, beat Johan Brunstrom of Sweden and Frederik Nielsen of Denmark 7-6 7-6.