The isothermal annealing behaviour of magnesium (Mg) alloy AZ31 deformed by multi-directional forging (MDF) at ambient temperature is investigated at temperatures ranging from 443 to 518 K. With increasing pass strain (Delta epsilon) in MDF, the recrystallization time curve shifts to shorter times. The Johnson-Mehl-Avrami-Kolmogorov (JMAK) exponent rises from 2.6 to 4.7, likely because microstructures with much higher density and finer twins evolve and are more homogeneously distributed at higher Delta epsilon. The activation energy and JMAK exponent for recrystallization are 120 kJ/mol and 2.6, and 58 kJ/mol and 4.7 at low- and high-temperature regions, respectively. The annealing process occurring after cold deformation is controlled by discontinuous recrystallization. In this research, this annealing process is discussed and compared with hot-deformed Mg alloy.