A method, system, and computer usable program product for on-demand monitoring of memory usage are provided in the illustrative embodiments. An indication of a memory leak in an application is detected where the application is operating in a data processing system and using a memory associated with the data processing system. An instruction to begin monitoring a memory usage of the application is received responsive to the detection. Responsive to receiving the instruction to begin, the memory usage of the application is monitored. An instruction to dump a data related to the monitoring is received and the data is dumped. An instruction to end the monitoring is received and the monitoring is ended. The detecting, the beginning, the dumping, and the ending may occur while the application remains in operation and while the application uses the memory. The memory leak is confirmed using the data.