This study analysed the determinants of fiscal deficit volatility of selected South Asian and Sub Saharan countries for the period 1990 to 2016. Generalize Method of Moments (GMM) is used to deal with problem of endogeneity. Results based on macroeconomic variables indicate that inflation, trade openness, foreign debts and real GDP per capita are the significant determinants of fiscal deficit volatility. Countries with high population growth associated with low fiscal deficit instability. Moreover results based on political and institutional variables indicate that low institutional quality (legal and bureaucracy), high internal and external conflicts, high ethnic and religious tensions and rising corruption may lead to high and persistent fiscal deficit volatility. The results of the current study leads to an important implication, that by improving quality of institutions, creating situations for economic stability and moving towards democratic regimes may ensure more stable fiscal deficits and resultantly positive effect on the long term economic growth. Supervisor:- Dr. Karim Khan