The German was forced off the court in his quarter-final with Mate Delic on Thursday, with bad light in Germany curtailing play with the score at 7-5 4-4 in Kohlschreiber's favour.
When play resumed in the ATP 250 clay court event on Friday, Delic immediately seized the initiative, holding his serve in game nine before breaking the number one seed in the next to level the match.
That was as good as it got for the Croatian, however, Kohlschreiber romping into a 4-0 lead in the decider before comfortably holding out to seal a 7-5 4-6 6-1 victory and progress to his semi-final against Denis Istomin.
Once there, he wasted little time in moving into an early lead, breaking the unseeded Uzebk twice to take the first set 6-2.
Istomin, who knocked out third seed Andreas Seppi in the quarter-final, hit back in the second set, claiming the crucial break in game 10 after a tense encounter that had seen all nine previous games go with the serve.
At that point, it seemed as if Istomin's extra energy would carry him through, but Kohlschreiber held firm and broke his opponent in game five of the deciding set.
From there, he had little trouble in seeing out victory, eventually sealing the win with his second match point to go through 6-2 4-6 6-4.
The German will now go up against the big-serving Karlovic in the final, after the Croatian needed two tie-breaks to see off Jiri Vesely 7-6 (8-6) 7-6 (9-7).
It could have been a wholly different story for seventh seed Karlovic, who found himself 6-4 down in the first-set tie-break before stringing together four consecutive points to steal the advantage away from his opponent.
And it was a similar story in the second, the Czech once again moving 6-4 ahead, only for Karlovic to take five of the next six points and secure his berth in the final.