Introduction: Celtra® Press is a zirconia-reinforced lithium silicate (ZLS) material. Ingots of ZLS are available in different translucency degrees. However, it is not known if the biaxial flexural strength differs between different translucency degrees. Aim: To evaluate the biaxial flexural strength of high translucent (HT), medium translucent (MT) and low translucent (LT) ZLS of different thicknesses. Material and methods: Sixty-three wax discs (14 mm in diameter) were fabricated by CAD/CAM. The LT and MT specimens were 0.5 mm, 1.0 mm or 1.5 mm thick, and the HT specimens were 0.5 mm thick. There were 9 discs in each group. These were heat-pressed with ZLS ingots, and then thermocycled, before loading to fracture. Biaxial flexural strength was measured in Newton and converted to MPa. Data analysis were done using One-way ANOVA and Tukey’s test (α = 0.05). Results: HT discs of 0.5 mm thickness (HT0.5) had significantly lower biaxial flexural strength (118.4 MPa, p ≤ 0.05) than LT1 (169.1 MPa), LT1.5 (173.8 MPa) and MT1.5 (169.6 MPa). The groups did not differ significantly between different degrees of translucency at equal thicknesses. Conclusions: Thickness and translucency degree is not critical for the flexural strength of low and medium translucent zirconia-reinforced lithium silicate (Celtra® Press), within thicknesses of 0.5 to 1.5 mm. The flexural strength is not affected by the translucency degree at a thickness of 0.5 mm, however further studies are needed to evaluate different thicknesses of high translucent zirconia-reinforced lithium silicate.