This paper investigates the causal relationship between financial development and economic growth in Sri Lanka for the period 1965 to 2013 using a trivariate vector autoregressive (VAR) framework that includes investment as an additional variable. This study utilized Per Capita Gross Domestic Product (GDP) and investment (as a measurement of indirect effect) as proxies for economic growth. Money supply, bank deposits and domestic credit to the private sector, each as a percentage of GDP were used as proxies for financial development. Data analysis involved Granger causality tests using the Johansen cointegration test and Vector Error Correction Model (VECM). Results show strong long-run Granger causality of financial development to economic growth in Sri Lanka. Furthermore, results suggest evidence of bi-directional short-run causalities between bank deposits and economic growth, and unidirectional causality from money supply to economic growth. The major implication of research findings is that enhancing financial sector development policies will improve productivity and drive long run economic growth in Sri Lanka.