Herein, we provide another twist to the connection between the epigenome and the epitranscriptome, by showing that cancer cells undergo promoter CpG island hypermethylation-associated transcriptional silencing of the 5-methylcytosine RNA methyltransferase NSUN7. Focusing on one of the most targeted tumor types by this epigenetic disruption, liver cancer, we characterized the completely undescribed activity of NSUN7 as a writer of the m5C mark in mRNA. Here, NSUN7 is linked to cancer.