Cometabolism describes the biodegradation of a contaminant by microorganisms grown on compounds other than the contaminant itself. Aerobic cometabolic degradation of 1,4-dioxane (14D) offers several advantages over metabolism-based biodegradation processes in which microorganisms use this compound as a sole source of carbon and energy for growth. These include (a) the use of widely distributed rather than highly specialized microorganisms (b) the ability to treat low, environmentally relevant concentrations (≤100 μg/L) of 14D, and (c), the ability to concurrently degrade chlorinated co-contaminants that are frequently encountered with 14D. This review summarizes recent studies highlighting these key features as well as field studies and emerging novel cometabolism-based approaches aimed at treating both 14D and its associated chlorinated co-contaminants.