Monocyclic phenolic compounds (MCPCs) from petroleum and coal sources mainly include phenol, cresols, and xylenols. A newly isolated 2,3-xylenol-degrading strain, Pseudomonas sp. XQ23, was found to be capable of degrading up to 10 MCPCs for the first time. Addition of easy-to-degrade MCPCs such as phenol and cresols helped decompose hard-to-degrade xylenols and the sequential digestion of the phenolic substrates was highly dependent on their molecule structures. The action on multiple MCPCs by the new isolate XQ23 from this work revealed useful clues on the co-biodegradation of multiple pollutants.