The paper provides an analysis on the impact of external sector openness and financial sector development on per capita income in the South Asian economies of Bangladesh, Bhutan, India, Nepal, Pakistan and Sri Lanka. For the annual series from 1980 to 2015, the instrumental variable model using a generalized method of moments (GMM) approach is estimated. The results show that liberalizing the external sector raises per capita income, conditional on the level of financial sector development. The large-economy influence analysis shows that India will benefit the most from external sector liberalization and other economies involved in this study still need to focus on financial sector development as opposed to on liberalizing capital flows. It further indicates that premature external liberalization in small and poor economies tends to be beneficial to the large neighbouring economy, which in this case is India, leading to resource exploitation. Accordingly, unless financial markets and institutions are strong enough to effectively deal with domestic resource mobilization, opening up the external sector alone may impede the economic development process.