Background: This study aimed to investigate the dimensional deformation that can occur during the fabrication of a 3D-printed aligner made with the TC-85 DAC resin (Graphy Inc., Seoul, Republic of Korea) and determine if the manual removal of the print supports before final aligner curing affects the dimensional accuracy. Methods: 10 subjects with permanent dentition were selected, and a set of aligners was digitally designed using the uDesign Direct Aligner beta software (Graphy Inc., Seoul, Republic of Korea). Each aligner was 3D-printed using TC-85 DAC resin (Graphy Inc., Seoul, Republic of Korea) twice: one copy was produced removing the print supports before final curing, whereas the other was cured with the supports still attached. The aligners were digitized and compared to the original design of the digitally designed aligner using RMS and Inter-second molar distance data to identify variations between 3D-produced aligners and their respective digital design. Results: the comparison between aligners produced in two different ways was statistically significant with a p-value < 0.0001 for both the records used. Conclusions: the manual removal of the print supports before final curing affects the dimensional accuracy of aligners made by direct 3D printing, permanently altering the aligner’s internal geometry, confirming that post-processing conditions significantly affect dimensional stability.