Mooring observations of nearly a full depth of the water column on the continental slope in the South China Sea reveal the ocean’s response to Typhoon Mangkhut (2018). Mangkhut induced sea surface cooling ~4 °C that biased to the right side of its track, which recovered with an e-folding time after approximately one week. Mangkhut was a relatively fast-moving typhoon and caused a fast near-inertial response throughout the entire depth in its lee. The typhoon-induced upper ocean (deep-water) near-inertial currents were greater than 1.5 m/s (~0.08 m/s), with an e-folding time of approximately a week (two weeks), and 1.04 (1.08) times the local inertial frequency. The near-inertial currents were near-circular polarized in the upper ocean and near-rectilinear polarized with the main axis in across-slope direction in deep water. However, the diurnal tide was near-circular polarized in the entire water column. The deep-water near-inertial waves amplified the vertical excursions of temperature and salinity excursions from ~120 m to ~200 m, which reduced the stratification, elevated vertical current shears, and enhanced turbulent dissipation rate, especially during September 14-17 when effects of near-inertial waves and diurnal tides overlapped. A net cooling ~0.15°C and salinity increase ~0.05 psu were observed in the deep ocean after Mangkhut. Typhoon-induced near-inertial waves may further contribute to the intensification of southwestward along-slope mean near-bottom currents. This study indicates the immediate influence of typhoon deep-water through near-inertial waves and its contribution to the bottom mixing on the continental shelf slope.