In the current work, the strain-rate dependent workability and flow instability has been investigated in a (Nb+V) stabilized microalloyed steel. Uniaxial compression tests were conducted in intercritical and single phase austenitic temperature domain (700–1100 °C) at several strain-rates (0.01–10 s−1), using a thermo-mechanical simulator (Gleeble®−3800). The results show that the flow stress increases at higher strain-rates. A good sample processing window arises at medium strain-rates (0.1–1 s−1); whereas, flow instability (serrations) at high (10 s−1) and low (0.01 s−1) strain-rate plastic deformations. After a detailed sample characterization, it appears that the reasons for flow instability during the hot and warm deformations are the formation of micro-cracks or void nucleation at low (0.01 s−1) strain-rate; whereas, flow localization and shear banding by adiabatic heating at a higher strain-rate (10 s−1). In both cases (0.01 and 10 s−1), the serration arises at periodic intervals with negative strain-rate sensitivity. At a higher strain-rate (10 s−1), the flow instability dominates till 1100 °C, because of relieving the deformation-induced stored energy mainly by dynamic recovery. At lower deformation temperatures (i.e., 700–800 °C), fine ferrite grains nucleate around shear bands by the diffusional transformation of austenite. The dynamic recrystallization is either absent or incomplete in agreement with the experimental determination of Tnr (non-recrystallization temperature) and texture analysis. The overall flow instability characteristics in terms of temperature, strain and strain-rate substantiate well with the dynamic materials model, by the superposition of flow instability and power dissipation efficiency, on revisiting the processing map.