In this study, poly(butylene terephthalate) (PBT)/halloysite composites having various amounts of halloysite, as a one-dimensional (1D) nanotubular alumina-silicate filler, were prepared by melt processing in a twin screw extruder. Nonisothermal crystallization behaviors of the samples were studied by DSC and XRD methods. The effect of halloysite amount on the nonisothermal melt crystallization kinetics of the PBT was analyzed with various kinetic models, namely the Ozawa, Avrami modified by Jeziorny, and Liu-Mo. Crystallization activation energies of the samples were determined by the Kissinger model. Viscoelastic properties of the samples were studied by DMA tests. By comparing the effect of halloysite amount on the melt crystallization kinetics of PBT, it was found that halloysite increased the crystallization rate of PBT. Crystallization activation energy values of the PBT and composite samples including 2%, 5%, and 10% of halloysite were found to be -341.8, -353.3, -373.6, and -419.6 kJ/mol, respectively. Based on the DMA tests, it was found that halloysite increased the elastic feature of the sample due to polymer-filler interactions.