This paper investigates the sewability of the woven denim fabrics based on needle penetration force (NPF). For this purpose, the effects of fabric weight, number of fabric layers, needle size, and the interaction effect of these parameters on NPF in twill denim fabrics were investigated. In addition, the influence of weave pattern on NPF was studied. The statistical analysis results show that NPF is influenced by these parameters. Fabric weight has a greater effect on NPF than other parameters. With increasing fabric weight, number of fabric layers, and needle size, the NPF increases. The trend of this increase is nonlinear as predicted by a cubic regression equation. The fabric sewability is also influenced by the mentioned parameters. The fabric sewability becomes poor with increasing fabric weight, needle size, and number of fabric layers. Generally, lighter fabrics sewn with finer needles have better sewability.