The purpose of this study was to examine three- and two-body wear values of flowable resin composites for posterior restorations, using a mechanical loading device. The cavities prepared on flattened extracted molars were restored with flowable resin composites (Clearfil Majesty LV: MLV, Estelite Flow Quick: EFQ, Beautifil Flow Plus F00: BFP, and MI Fill: MIF) using accompanying adhesive systems. A universal resin composite (Clearfil Majesty) was used as a control. The specimens were subjected to in vitro three- and two-body wear testing. MLV showed high wear value (three-body: 14.69 µm, two-body: 0.268 mm³) compared with other materials tested in both three- and two-body wear tests. BFP showed high three-body wear value (5.78 µm), whereas low two-body wear value (0.008 mm³). MIF and EFQ showed equivalent wear values (MIF, three-body: 0.42 µm, two-body: 0.026 mm³; EFQ, three-body: 1.15 µm, two-body: 0.14 mm³) to that of the control in both wear tests.