M'-type Nd³⁺:GdTaO₄ microcrystals, synthetized by a molten salt synthesis method, were investigated via temperature-/pressure-dependent photoluminescence measurement. In the test temperature range 293-373 K, the spectral positions of emissions from ³F_3/2→⁴I_9/2 transition exhibit high thermal stabilities. The temperature coefficient of ³F_3/2(R₂)→⁴I_9/2(Z₅) transition is only 0.003 9 cm^-1·K^-1. The intensity ratio between transitions of ³F_3/2(R₂)→⁴I_9/2(Z₂) and ³F_3/2(R₁)→⁴I_9/2(Z₂) has a large temperature dependence, and its relative sensitivity in the physiological temperature range is (0.60-0.52)(%·K^-1). In the test pressure range 10⁵ Pa-11.39 GPa, all the transitions linearly shift with pressure. The spectral position of ³F_3/2(R₂)→⁴I_9/2(Z₅) transition is very sensitive to pressure, with a sensitivity of 15.18 cm^-1·GPa^-1. The intensities and spectral widths of the transitions in the heating and compression processes were also analyzed. Compared with the other optical sensors in the near-infrared wavelength range, the good performance of M'-type Nd³⁺:GdTaO₄ in temperature and pressure sensing was revealed.