According to an embodiment, a detection system includes a detection device, an acoustic emission sensor, and a processing unit. The detection device detects a change that occurs in a structure or a change in an environment related to the structure. The acoustic emission sensor detects an acoustic emission wave produced from the structure. The processing unit performs first signal processing to process an acoustic emission signal indicating the acoustic emission wave, which is input from the acoustic emission sensor until a first period of time elapses after a detection signal is input from the detection device. The detection signal indicates that a change has occurred in the structure or the environment related to the structure.