Knowledge about the strength of restorative materials is crucial to a proper decision-making process on oral rehabilitation. Various test set-ups can determine the strength of materials under different circumstances, however, not much is known about materials’ behavior under higher or more abrupt loads, such as in an impact situation. This study aimed to investigate the effect of different consistencies of resin composite materials (Conventional and Flowable) commonly used for dental restorations on their impact strength. Specimens of two light-cured composites (Flow - Clearfil Majesty ES Flow, Kuraray Noritake; Conv - Clearfil AP-X PLT, Kuraray Noritake) were produced with two different thicknesses (1.0 or 1.5 mm; n=15) to be tested under impact. The impact strength was measured within the Dynstat method. Data were analyzed by one-way ANOVA. The statistical significance was set to p<0.05. The results showed a significant difference between Flow and Conv for 1.0 mm thickness (Flow [11.61±2.66 kJ/m²]; Conv [5.06±0.98 kJ/m²]), but no significant difference was found between materials with 1.5 mm thickness (Flow [6.53±1.04 kJ/m²]; Conv [6.75±1.01 kJ/m²]). Considering thicknesses in the same materials, higher impact strength values were found for the Flow composite with 1.0 mm thickness. This finding can point to a higher population of defects in larger volumes of composite materials. Given the results, it can be concluded that the evaluated flowable resin composite behaved similarly to a regular composite in thicker constructions and that inner defects and residual polymerization shrinkage stresses can make larger pieces more fragile.