Metal halide perovskites have been intensively studied over the past years due to their attractive electronic, optical and optoelectronic properties. In spite of the phenomenally high solar-conversion efficiency achieved with perovskites, their adverse instability remains the key obstacle restricting their wider applications. These ionic crystals can be affected by many factors, such as varied temperatures, humid air, polar solvents, and electron-withdrawing/donating gases. However, under certain controlled conditions, changes in perovskite structures/compositions via, for example, phase transitions, hydration/ dehydration, gas adsorption/desorption, and ion intercalation/decalation, can all be reversed, suggesting their great potential for sensing applications. In this contribution, we first overview recent investigations and mechanistic studies on the stability of metal halide perovskites under various environmental conditions. Then, we highlight the recent attempts to apply perovskites for the detection of temperature change, humidity, gases, solvents and ions. Finally, we discuss current challenges and future opportunities for developing sensing systems based on metal halide perovskites.