Like in his second-round victory over American Steve Johnson, when Thiem had to come back from a two-set-to-one deficit, the Austrian lacked sharpness from the baseline and was inconsistent with his serve in the early part on Friday.
But he rallied in the second set, improving his play both in the rallies and his returns to even the match at a set apiece, reports Efe news.
The turning point in the contest was the third set tie-breaker, when Thiem came up with some clutch winners and aces to seize control on the Grandstand.
For the match, Thiem struck 18 aces and 59 winners, compared with 13 aces and 44 winners for Fritz.
The Austrian was able to secure the victory in three hours and 19 minutes despite committing more unforced errors than his opponent (52-37).
Thiem, who also defeated Fritz in four sets in last years US Open, will next take on either fifth-seeded South African Kevin Anderson or 28th-seeded Canadian Denis Shapovalov.
In other third-round mens singles action Thursday afternoon, Georgias Nikoloz Basilashvili defeated Argentinas Guido Pella 6-3, 6-4, 1-6, 7-6 (7-4).
The Georgian will next square off in the round of 16 against either Spanish world No. 1 and defending champion Rafael Nadal or Russian No. 27 seed Karen Khachanov.Read More