An 1892.4 nm ultrafast passive Q-switched fiber laser is demonstrated by using Thulium-doped fiber (TDF) in conjunction with a multi-walled carbon nanotubes (MWCNTs) as a saturable absorber (SA). The MWCNTs film is sandwiched between two FC/PC fiber connectors and integrated into the laser cavity with 802 nm pump for Q-switching pulse generation. The pulse repetition rate can be tuned from 3.8 to 4.6 kHz while the corresponding pulse width reduces from 22.1 to 18.4 μs as the pump power is increased from 187.3 to 194.2 mW. A higher performance Q-switched Thulium-doped fiber laser (TDFL) is expected to be achieved with the optimization of the MWCNT-SA saturable absorber and laser cavity.