Rice is one of the most important food crops in the world, and its growth, development, yield, and grain quality are susceptible to a deficiency of the macronutrient potassium (K+). The molecular mechanism for K+ deficiency tolerance remains poorly understood. In this study, K+ deficient conditions were employed to investigate the resulting changes in the transcriptome of rice seedling roots. Using ribonucleic acid sequencing (RNA-Seq) and analysis, a total of 805 differentially expressed genes were obtained, of which 536 genes were upregulated and 269 were downregulated. Gene functional classification showed that the expression of genes involved in nutrient transport, protein kinases, transcription processes, and plant hormones were particularly altered in the roots. Although these changes were significant, the expression of most genes remained constant even in K+-deficient conditions. Interestingly, when our RNA-Seq results were compared to public microarray data, we found that most of the genes that were differentially expressed in low K+ conditions also exhibited changes in expression in other environmental stress conditions.