Magnesium aluminate (MgAl_z0₄) doped with terbium was prepared by combustion synthesis. Defect centres of MgAl_z0₄:Tb are studied by correlating various techniques such as Electron Spin Resonance (ESR), Thermoluminescence (TL) and Optically Stimulated Luminescence (OSL). TL studies on MgAl_z0₄:Tb³⁺ show two TL peaks at 120 and 340°C. MgAl_z0₄:Tb³⁺ exhibits OSL when stimulated with 470 nm blue light. ESR study shows two defect centres with g = 2.011 and g = 2.0052 which are assigned to V- centre and F⁺ centre, respectively. Step annealing ESR technique study suggests that V -centre is correlated to 120°C TL peak whereas F⁺ centre is correlated with both the 120 and 340°C TL peaks. A TL mechanism is proposed. ESR-OSL correlation studies are carried out. The results of ESR-OSL correlation study along with TL bleaching study support the proposed TL mechanism of 120°C TL peak.