Serious shrinkage and warpage are obstacles to the development of ideal isotactic polypropylene (iPP) materials for polymer-based powder bed fusion (PBF) technique. In this work, the variations of the dimensional accuracy of the PBF-printed iPP parts were investigated with various printing parameter and nucleating agent. The iPP parts printed at a scanning speed of 700 mm/s exhibit smaller extents of shrinkage and curling than those at lower speeds, due to a lower degree of crystallinity. Interestingly, iPP blended with the α- or β-nucleating agent demonstrates more serious part deformation with respect to neat iPP. Especially, α-nucleating agent tends to trigger the most severe curling under the investigated printing parameters. Based on X-ray diffraction and differential scanning calorimetry (DSC) results, both neat iPP and α-iPP parts crystallize into α-crystal, while β-iPP parts display the coexistence of β- and α-crystals. And, the difference of the crystallinity is less than 3% in three specimens. This suggests that both crystallinity and crystalline structure are not the main reasons for the shrinkage and warpage in this case. Instead, the severe part deformation of the α-iPP parts is assigned to the narrower sintering window as well as the higher onset crystallization temperature of α-iPP, which hinder relaxation of residual stresses. This work provides insights into the part deformation mechanism for PBF-processed polymer materials.