The Cs atoms are prepared in the 6D state by two-photon absorption. CsH(X1Σ+, v″=0) is generated from the Cs(6D)+H2 reaction. By overtone excitation with a pulsed dye laser, highly vibrational states v″ ≥ 15 of CsH in its ground electronic state are obtained. A diode laser is used to probe either the prepared vibrational state or the collisionally populated states. The decay signal of the time-resolved fluorescence from the A1Σ+(v′) → X1Σ+(v″) transition is monitored. Based on the Stern—Volmer equation, the total rate coefficients for v″ = 15–22 are yielded. The time evolution and relative intensities of three related states, v″, v″ − 1 and v″ − 2, made by the initially prepared v″ state of CsH are measured. Rate coefficients of single- and double-quantum relaxation are obtained. These results show that single-quantum relaxation accounts for ≥50% of the total relaxation out of states v″=17–20. Multiquantum relaxation (Δv≥2) makes major contribution (≥62%) to the vibrational relaxation at v″=21 and 22. A simple explanation is given.