Pepper is widely cultivated, and the application of CO 2 promotes photosynthesis and increases its yield. However, the molecularmechanisms underlying this are still unclear. In this study, the photosynthetic correlation indexes under elevated CO 2and control conditions were compared. The application of CO 2 increased the photosynthetic capacity of pepper. Moreover,RNA-Seq analysis was used to identify genes that were diff erentially expressed between pepper leaves grown in CO 2 -enrichedconditions and those grown in control conditions. The 149 diff erentially expressed genes (DEGs) were found to be involvedin photosynthesis and other metabolic processes. According to GO signifi cant enrichment analysis, the proteins encodedby the DEGs were mainly found to be located in the chloroplast, the chloroplast matrix, and the apoplast. According toKEGG signifi cant enrichment analysis, the DEGs were found to be involved in glutathione metabolism; starch and sucrosemetabolism; and stilbenoid, diarylheptanoid, gingerol, fl avonoid, and phenylpropanoid biosynthesis. The DEGs were alsoinvolved in the pentose phosphate pathway, carbon metabolism, and porphyrin and chlorophyll metabolism. Based on theGO annotation and the KEGG database analysis, ten of the DEGs identifi ed were suggested to be involved in photosynthesisand related processes; these genes were predicted to have roles in carbohydrate, soluble sugar, and glutathione metabolism,and in raffi nose, cysteine, nucleotide, and ABA biosynthesis. These DEGs are involved in the pentose phosphate pathwayand tricarboxylic acid cycle of carbon assimilation during photosynthesis. One of the DEGs was also found to be involved inchlorophyll biosynthesis. These results lay the foundation for further investigation of the molecular mechanisms and genesinvolved in the response to CO 2 enrichment in peppers.