Inclement weather at the ATP 250 clay-court event in Austria has disrupted the schedule this week, so home hope Thiem had to play both his quarter-final and last-four contests on the same day.
The Austrian was unperturbed, though, as he reached his first ATP tour final and will attempt to win his maiden title by beating the in-form David Goffin on Saturday.
First up was a clash with second seed Granollers, an opponent Thiem had already beaten twice on the red surface this season, and he duly delivered a third win courtesy of a 6-4 7-5 triumph.
The fifth seed did not have it all his own way as he was broken on three occasions, but he claimed five breaks of his own to progress in an hour and 46 minutes, ending Granollers' defence in the process.
Monaco - the runner-up last year - was also in action twice on Friday and ousted fourth seed Andreas Seppi in three sets to set up his clash with Thiem.
However, the Argentina native wilted in the semi-final as Thiem - who fired down six aces - came through 6-3 6-1 in less than an hour.
There is guaranteed to be a first-time winner on the ATP Tour on Saturday after Goffin - who won twice on Thursday - reached his first Tour final by coming from behind to defeat Maximo Gonzalez 5-7 6-4 6-3.
Since losing to Andy Murray in the first round of Wimbledon in June, Goffin has won 19 straight matches, which has seen him collect three ATP Challenger Tour titles.
Goffin may have landed just 52 per cent of first serves, but when he got that right Gonzalez had no answer as the Belgian won 36 of 48 first-serve points.