Previously, we have shown that the effects of the coating solution concentration of coupling agent on the interlaminar shear strength of fiber/epoxy composites were best investigated with 4 wt.% nano-CaCO 3 content. Here, five different types of composites were prepared: (E–0–4): composites modified by untreated nano-CaCO 3 , (E–1.1–4): composites modified by nano-CaCO 3 with 1.1 wt.% coating solution concentration treatment. Similarly, samples E–2.3–4, E–3.5–4 and E–4.6–4 were also fabricated. The results show that nanocomposites prepared with 2.3 wt.% and 3.5 wt.% coating solution concentration treatment have the best shear properties, including interlaminar shear strength, elongation at break and fracture work. With 2.3 wt.% coating solution concentration treatment, these have values of 142.4 MPa, 1.95 mm and 1.86 J, which can increase 11%, 41% and 39% compared to the composite prepared with untreated nano-CaCO 3 , respectively.