N⁶-adenosine methylation (m⁶A) is the most abundant mRNA modification that controls gene expression through diverse mechanisms. Accordingly, m⁶A-dependent regulation of oncogenes and tumor suppressors contributes to tumor development. However, the role of m⁶A-mediated gene regulation upon drug treatment or resistance is poorly understood. Here, we report that m⁶A modification of mitogen-activated protein kinase 13 (MAPK13) mRNA determines the sensitivity of cancer cells to the mechanistic target of rapamycin complex 1 (mTORC1)-targeting agent rapamycin. mTORC1 induces m⁶A modification of MAPK13 mRNA at its 3' untranslated region through the methyltransferase-like 3 (METTL3)-METTL14-Wilms' tumor 1-associating protein(WTAP) methyltransferase complex, facilitating its mRNA degradation via an m⁶A reader protein YTH domain family protein 2. Rapamycin blunts this process and stabilizes MAPK13. On the other hand, genetic or pharmacological inhibition of MAPK13 enhances rapamycin's anticancer effects, which suggests that MAPK13 confers a progrowth signal upon rapamycin treatment, thereby limiting rapamycin efficacy. Together, our data indicate that rapamycin-mediated MAPK13 mRNA stabilization underlies drug resistance, and it should be considered as a promising therapeutic target to sensitize cancer cells to rapamycin.