Abnormal translation of the MYC proto-oncogene is a hallmark of the initiation and maintenance of tumorigenesis. However, the molecular mechanism underlying increased MYC protein levels in certain cancer types without a corresponding increase in MYC mRNA levels is unclear. Here, we identified a novel lncRNA, MTAR1, which is critical for post-transcriptional regulation of MYC-induced tumorigenesis. MTAR1 is essential for recruiting IGF2BPs into PABP1-mediated liquid–liquid phase separation (LLPS) complexes and facilitates IGF2BPs-mediated MYC mRNA translation. MTAR1 enhanced binding between IGF2BPs and PABP1, thereby promoting MYC mRNA stability and increased MYC mRNA translation. In summary, MTAR1 is a novel MYC-related lncRNA that contributes to tumor progression by enhancing MYC translation through mediating PABP1/IGF2BPs liquid–liquid phase separation.