The mechanical and physical properties of biodegradable magnesium (Mg) alloys make them suitable for temporary orthopaedic implants. The success of these alloys depends on their performance in the physiological environment. In the present work, surface modification of Mg-Ca binary alloy by acid pickling for better biomineralization and controlled biodegradation is explored. The corrosion rates of nitric and phosphoric acid treated samples were analysed by conducting electrochemical corrosion tests. In vitro degradation behaviour was studied using immersion test in simulated body fluid (SBF). The sample surfaces were characterized using scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). It is seen that acid pickling leads to significant improvement in biomineralization and develop in situ calcium phosphate (CaP) coating on the sample surfaces. In addition, the treated samples recorded a reduced degradation rate in the SBF compared to untreated samples. Thus, acid pickling is suggested as an effective surface treatment method to tailor the biomineralization and degradation behaviour of the Mg-Ca alloy in the physiological environment.