We determined the diet of Emydura krefftii, an abundant and widespread omnivorous freshwater turtle in north-eastern Australia, in an artificial urban impoundment. A potentially significant dietary influence is feeding of bread to the turtles by members of the public. This has led to the formation of a dense aggregation of the species at one end of the impoundment. The most substantial component of the diet by volume was the introduced weed Cabomba. Bread and figs were also important but only in specific locations. Bread was offered to turtles at the feeding aggregation in amounts close to the maximum eaten by captive turtles, and thus probably negatively influences nutrient status. Animal matter (insects, vertebrate carrion) was only a small proportion of the diet. We quantified intake, digestibility and transit time in the laboratory for four commonly occurring dietary items. Fish and bread were the most highly digestible food items and passed quickly through the gut. Despite its contribution to the diet in the wild, captive turtles ate little Cabomba, and it passed slowly through the gut and was poorly digested. Future research on interactive effects between diet items on digestive performance is recommended to understand the performance of turtles on apparently poor-quality diets.