The high temperature deformation behavior of a Mg-5wt.%Y (Mg–5Y) binary alloy has been investigated using uniaxial compression test in the temperature range of 523 K–723 K and strain rate of 0.001 s-1 - 10 s-1. The true stress-strain curves depict that flow stress significantly decreases with the increase in temperature and decrease in the strain rate and vice-versa. An Arrhenius based hyperbolic sine equation was used to model the flow stress of the alloy at high temperature. Processing maps were developed for true strains of 0.25 and 0.45, which represent the strain near the peak stress and steady-state region, respectively. The safe region is found to be in the strain rate range of 0.001 s-1 – 0.1 s-1 and temperature range of 623 K–723 K, while the unstable region is found to be in strain rate range of 1 s-1 – 10 s-1 at a temperature range of 523 K–723 K. In the safe region, characterization of deformed microstructures using electron backscatter diffraction (EBSD) shows that the prominent deformation mechanism is continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX) with manifestation of twin induced DRX and particle stimulated nucleation (PSN). The unstable region, however, consists of cracks, voids and deformation twins with little evidence of DRX.