Histone modifications, especially H3K27 and H3K36 methylations, are crucial for epigenetic regulation and are often dysregulated in cancer. In a comprehensive analysis of 11,194 patient samples across 32 cancer types, we identified significant genomic alterations in H3K27 and H3K36 modifiers, with the most common being in KDM6B, BRPF1, KDM6A, SETD2, and NSD1. Patients with these alterations also frequently exhibited mutations in genes like TP53 and PIK3CA. Moreover, the presence of these histone modifier alterations correlated with poorer overall survival, emphasizing their potential as both oncogenic drivers and prognostic markers in various cancers.