We demonstrate a passively Q-switched Tm-doped fiber laser with carbon nantubes (CNTs), yielding a maximum output average power of around 82 mW and the corresponding pulse energy of 1.2 \mu J. The laser operates at ~1.985 \mu m with repetition rates ranging from 26 to 69 kHz and pulse-duration from 1.5 to 2.6 \mu s. Our proposed laser shows that the CNTs are promising for the potential Q-switched Tm-doped fiber laser with high energy and tunable wavelength operation. To the best of our knowledge, this is the first report of a Q-switched Tm-doped fiber laser with CNTs as saturable absorber.