Exploring TiO2‐photocatalysts for sunlight conversion has high demand in artificial photosynthesis. In this work, edge‐enriched ultrathin molybdenum disulfide (MoS2) flakes are uniformly embedded into the bulk of yolk‐shell TiO2 as a cocatalyst to accelerate photogenerated‐electron transfer from the bulk to the surface of TiO2. The as‐formed MoS2/TiO2 (0.14 wt%) hybrids exhibit a high hydrogen evolution rate (HER) of 2443 µmol g−1 h−1, about 1000% and 470% of that of pristine TiO2 (247 µmol g−1 h−1) and bulk MoS2 decorated TiO2 (513 µmol g−1 h−1). Such a greatly enhanced HER is attributed to the exposed catalytic edges of the ultrathin MoS2 flakes with a robust chemical linkage (TiS bond), providing rapid charge transfer channels between TiO2 and MoS2. The catalytic stability is promoted by the antiaggregation of the highly dispersed MoS2 flakes in the bulk of yolk‐shell TiO2. The exponential fitted decay kinetics of time‐resolved photoluminescence (ns‐PL) spectra illustrates that embedding ultrathin MoS2 flakes in TiO2 effectively decreases the average lifetime of PL in the MoS2/TiO2 hybrids (τave = 4.55 ns), faster than that of pristine TiO2 (≈7.17 ns) and the bulk MoS2/TiO2 (≈6.13 ns), allowing a superior charge separation and charge trapping process for reducing water. Chemical bonding of ultrathin MoS2 flakes mediates the electron transfer channel from the bulk to the surface of crystal TiO2. Embedded ultrathin MoS2 effectively suppresses charge trapping and shows excellent photoactivity and high stability with the increasing exposed catalytically edges. The transient fluorescence kinetics confirms the prolonged lifetime of photogenerated active electrons in an MoS2/TiO2 composite.