Significance Posttranslational modifications (PTMs) on histone lysines regulate gene expression and physiological functions. Succinylation is a newly discovered PTM with distinctive features. However, rarely studies have shown the function of succinylation on histone lysines. Our biochemical and structural studies demonstrate that GAS41, an oncogene-coded protein, can act as the reader of succinylation on histone H3K122. The functional significance of the pH-dependent histidine of GAS41 recognizing succinyl lysine (Ksuc) could have implications in local pH-dysregulated circumstances. The mechanism illustrated by the structures also provides an important insight into the development of specific regulators targeting the GAS41 YEATS domain in the future.