Objective: All-ceramic restorations are becoming more common in prosthetic treatment. The material composition of the ceramics provides different properties in terms of strength, aesthetics, translucency. The aim of the study was to assess whether the variation in material composition and production methods affects the internal fit of monolithic zirconia crowns. The null hypothesis was that different material compositions and production methods will not affect the internal fit, given that all other factors such as preparation type, crown shape and crown thickness are the same. Material and methods: Sixty-six zirconia crowns were produced from five different commercial manufacturers to a premolar model tooth with shallow circumferential chamfer preparation. Internal fit was assessed by the replica method. Results: There was a statistically significant difference in the occlusal internal fit values for the different groups (Kruskall Wallis, p = 0.0003). The soft machined crowns in three groups (BX, DD and ZZ) had a thicker occlusal cement space than all the other groups. There was no statistically significant difference in marginal and axial internal fit values among the different groups. Conclusion: The production method for monolithic zirconia crowns has an effect on internal fit. The largest variation was observed occlusally in soft machined crowns. Excess occlusal cement accumulation leads to increased axial discrepancy which can further give both technical and biological effect. Material composition did not had a clear correlation with the internal fit of the tested zirconia crowns.