The impact of investor sentiment on stock market price has been a subject of long standing interest to both economists and practitioners. Following the theoretical argument of behavioral asset pricing, recent literature confirms the possible linkage between the aggregate investor sentiment and stock returns. In this paper we examine the causal relationship between investor sentiment index constructed from various market related implicit proxies, and aggregate stock market indices such as BSE sensex and NSE Nifty indices. The Johansen co-integration test is applied to measure the long-term relationship between the sentiment index and market indices and Error Correction Method has been used to check the short-term relationship between the two variables. Granger causality test is used to check the causal relationship between them. Our results suggest that, given the evidence of comovements of sentiment and market index there is significant long-run and short-run relationship between the two indices. Consistent with the existing literature which suggest that the sentiment effect is a short-run phenomena, our findings gives an indication that long term investment strategy can effectively mitigate the sentiment risk. The results for causality test suggest that there exist a unidirectional causal relationship between the sentiment index and market indices.