An integrated spectral pyrometry (ISP) technique particularly well suited to monitor the temperature of small bandgap semiconductors during molecular beam epitaxial growth is proposed. The technique relies on integrating the thermal radiation power emitted by the wafer over a spectral range where it is fully opaque, so as to avoid contribution from radiation transmitted from the substrate heater. In the present work, a 900–1700 nm array InGaAs spectrometer normally employed for band-edge thermometry was used. The temperature dependence of the integrated signal can be expressed by an Arrhenius-type exponential relation. The calibration procedure and the method employed to compensate for the background radiation from other hot objects in the reactor is discussed. The ISP performance is then demonstrated by monitoring the temperature during the growths of a Si doped InAs layer on InAs substrate and of an InSb/AlInSb quantum well structure on GaAs substrate. The ISP technique allows reproducible wafer temperature monitoring down to about 200 °C.