This paper reports the simultaneous measurements of multiple flow parameters in a scramjet facility operating at a nominal Mach number of 2.5 using a sensing system based on tunable diode-laser absorption spectroscopy (TDLAS). The TDLAS system measures velocity, temperature, and water vapor partial pressure at three different locations of the scramjet: the inlet, the combustion region near the flame stabilization cavity, and the exit of the combustor. These measurements enable the determination of the variation of the Mach number and the combustion mode in the scramjet engine, which are critical for evaluating the combustion efficiency and optimizing engine performance. The results obtained in this work clearly demonstrated the applicability of TDLAS sensors in harsh and high-speed environments. The TDLAS system, due to its unique virtues, is expected to play an important role in the development of scramjet engines.