Purpose: To evaluate the effect of food-simulating liquids (FSLs) on the mechanical properties of provisional restoration materials fabricated by 3D printing, milling, and traditional fabricating methods. Materials and Methods: The bar specimens were fabricated with traditional, milling, and 3D-printing methods according to ISO 10477 specifications. Each group of specimens was randomly subdivided into four groups to be immersed in various FSLs: distilled water (control group), n-heptane, 50% ethyl alcohol, and 0.02 mol/L citric acid for 7 days at room temperature (n = 19 per group). The Knoop hardness (KHN) was evaluated, and the specimens were subjected to a three-point bending (3PB) test to evaluate flexural strength (FS) and flexural modulus (FM). One-way ANOVA and Tukey tests were used to analyze the data. Results: Fabrication methods had a significant effect on the mechanical properties of the materials being tested. FSLs had no effect on the FS and FM of materials being tested. The 50% ethyl alcohol solution significantly decreased the hardness of traditional group specimens, and the n-heptane and 50% ethyl alcohol solutions increased the hardness of the 3D-printed specimens significantly (P ≤ .05). Scanning electron microscopy (SEM) revealed that while traditional and milling group specimens showed a ductile fracture type, 3D-printed specimens showed a brittle fracture type. Conclusions: Production methods affected the mechanical properties of provisional restoration materials. Immersion in 50% ethyl alcohol solution decreased the KHN of the traditional specimens. FSLs had no negative effect on the mechanical properties of the milled and 3D-printed specimens.