We demonstrated a pulsed ytterbium all-fiber laser passively Q-switched using excited-state absorption of thulium fiber and a mode-field-area mismatch. The absorption cross section of the excited state ^3F_4 was measured and determined to be the key factor inducing pulsing, and it was much higher than that of the ground state ^3H_6 over 0.95–1.15 µm. By successfully realizing the pulsed laser at 1030 nm, which is the most critical wavelength for Q-switching, we verified that the excite state ^3F_4 of Tm^3+ could be a full-range saturable-absorber Q-switch for a Yb fiber laser over 1.0–1.15 µm.