Deep level transient spectroscopy (DLTS) measurements have been conducted on MBE-grown heterostructure InSb/In1-xAlxSb diodes. The measurements were conducted in the temperature range 10-130 K and two majority carrier (electron) traps, labelled E1 and E2, have been observed. A trap signature has been produced from the DLTS spectra for both traps. The activation energies determined from Arrhenius plots of the peak temperatures as a function of rate window for E1 and E2 were 17 meV and 79 meV, respectively. The apparent capture cross-sections and concentrations for E1 and E2 have also been measured.