In the present study, we prepared solid dispersions of the poorly water-soluble drug nitrendipine (NIT) using the twin screw extruder method with high-molecular-weight substances, hydroxypropylmethylcellulosephthalate (HPMCP) and Carbopol (CAR), as carriers. Powder X-ray diffraction (PXRD) and differential scanning calorimetry (DSC) evaluation showed that solid dispersions can be formed when NIT–HPMCP and NIT–CAR mixtures are treated with the twin screw extruder method. Fourier Transformation IR Spectroscopy (FT-IR) obtained with NIT–HPMCP and NIT–CAR solid dispersions indicated the presence of hydrogen bonding between the drug and the carriers. NIT–CAR solid dispersions were found to give somewhat higher dissolution than crystalline NIT and physical mixtures, while the dissolution of NIT–HPMCP solid dispersions was markedly decreased compared with the crystalline NIT and physical mixtures. These findings indicated that CAR has a greater ability to improve the dissolution of NIT than HPMCP when a twin screw extruder was employed to prepare the solid dispersions. The twin screw extruder method can be used as a simple and effective method for the preparation of solid dispersions to improve the dissolution properties of poorly water-soluble drugs when choosing proper polymers as carriers.