In this Letter, we report, to the best of our knowledge, the first demonstration of an in-band pumped gain-switched Dy3+-doped fiber laser operating at 3.24 µm. The monolithic cavity bounded by two fiber Bragg gratings was pumped by a gain-switched Er3+-doped fiber system. It produced stable nanosecond pulses in a single-pulse regime on its entire operating range from 20 kHz to 120 kHz. A record average power of 1.43 W was achieved for a repetition rate of 120 kHz, and a record pulse energy of 19.2 µJ was achieved at 60 kHz. These results represent a significant improvement in Dy3+-doped pulsed fiber laser performances and open the way to applications in the fields of remote sensing and material processing.