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The aim of the study was to assess the degree of conversion (DC), microhardness, polymerization shrinkage stress (PSS) and volumetric contraction of two bulk-fill composites (SonicFill, Kerr Corporation, Orange, CA, USA - (SF) and Filtek BulkFill, 3M ESPE, St Paul, MN, USA - (FB)) and one conventional nanofiller resin composite (Z350XT – 3M ESPE, St Paul, MN, USA) inserted incrementally (Z350I) or in bulk (Z350B). Micro-Raman spectroscopy, Knoop microhardness, PSS test and micro-computed tomography technique (μCT) were used to evaluate the resin composites. Data were analyzed with one-way ANOVA followed by Tukey’s post hoc test (α = 0.05). DC was not affected by the type of the composite, excepted when conventional resin composite was inserted in a single increment (p = 0.002). FB and Z350I showed higher microhardness values than Z350B (p = 0,003), while SF showed no statistically significant difference to the other resin composites. No statistical differences were found among the composites regarding to PSS (p = 0.104) and volumetric shrinkage (p = 0.258). Therefore, it can be concluded that bulk-fill and conventional resin composites tested present similar properties. Thus, shorter time required for the use associated with simplified operative technique are considered clinical advantages of bulk-fill composites.