Cellulose synthase-like (CSL) proteins belonging to glycosyltransferase family 2 (GT2) are believed to be involved in the biosynthesis of cell wall polymers. The CSLD subfamily is common to all plants, but the functions of CSLDs remain to be elucidated. We report here an in-depth characterization of a narrow leaf and dwarf1 (nd1) rice mutant that shows significant reduction in plant growth due to retarded cell division. Map-based cloning revealed that ND1 encodes OsCSLD4, one of five members of the CSLD subfamily in rice. OsCSLD4 is mainly expressed in tissues undergoing rapid growth. Expression of OsCSLD4 fluorescently tagged at the C- or N-terminus in rice protoplast cells or Nicotiana benthamiana leaves showed that the protein is located in the endoplasmic reticulum or Golgi vesicles. Golgi localization was verified using the phenotype-rescued transgenic plants expressing OsCSLD4-β-glucuronidase (GUS) under its own promoter. Two phenotype-exhibiting tissues, culms and root tips, were used to investigate the specific wall defects. Immunological studies and monosaccharide compositional and glycosyl linkage analyses explored several wall compositional effects caused by disruption of OsCSLD4, including alterations in the structure of arabinoxylan and content of cellulose and homogalacturonan, which are distinct in the monocot grass-species rice. The incongruous alterations in the two tissues and the observable structural defects in primary walls indicate that OsCSLD4 plays important roles in cell wall formation and plant growth.