Background/Objectives: Clear cell renal cell carcinoma (ccRCC) is the most common form of kidney cancer. Human ccRCCs have increased glycolytic metabolism and decreased mitochondrial oxidative metabolism relative to normal kidneys. Our research using human RCC4 ccRCC cells and a murine model of ccRCC, TRACK (TRAnsgenic model/Cancer/Kidney), in which a triple-mutant (P402A, P564A, N803A) human HIF1α is selectively expressed in proximal tubule cells (PTCs), revealed highly induced ATF4, a stress-responsive transcription factor. We then investigated the role of ATF4 in the metabolic changes in ccRCC. Methods: We performed comprehensive analysis of the ccRCC Cancer Genomics Atlas (TCGA) data. We deleted ATF4 in PTCs of TRACK mice and human RCC4 cells. We conducted genome-wide transcriptomic and untargeted metabolomic studies of cortices of WT and CGERA∆T (TRACK mice with PTC-specific ATF4-knockout (KO)) mice and performed glucose isotopologue tracing in parental and ATF4 KO RCC4 cells. Results: Analysis of TCGA data showed increased mRNAs of enzymes in glycolysis and reduced mRNAs of enzymes in the TCA cycle. Transcriptomic and metabolomic studies demonstrated that ATF4 deletion suppressed glycolysis and enhanced TCA cycle metabolism in CGERA∆T versus WT cortices. Glucose isotopologue tracing showed that ATF4 deletion altered glycolysis pathway metabolite levels and shifted glucose metabolism towards the TCA cycle, evidenced by increased intracellular [13C2]citrate in RCC4-ATF4 KO cells. Using the Seahorse XFe96 analyzer we also showed reduced glycolytic capacity and reserve in RCC4-ATF4 KO cells. Conclusions: Collectively, our results demonstrate that ATF4 regulates glycolysis in ccRCC, supporting ATF4 as a therapeutic target.