Empirical research on the profitability of momentum investment strategies in emerging equity markets has presented mixed findings and therefore the momentum patterns in emerging equity markets have not been explained to the unanimous satisfaction of the researchers. This research examines the momentum returns and their determinants for stocks listed on Pakistan Stock Exchange using the data from 2001 to 2015. The analysis is also performed for the two sub-periods, from 2001 to 2007 and from 2009 to 2015, and the two sub-samples, financial firms and non- financial firms. Results show that over the complete sample period the momentum returns are positive and as high as the returns reported in early literature (for example, Jegadeesh & Titman, 1993), but they are not statistically significant. Similar results are obtained for the two sub-samples; however, for the two sub-periods, the momentum strategy yields completely contrasting results. For the first sub-period which experienced a high economic growth, low inflation and better governance, the momentum portfolios earned significant positive returns; whereas for the second sub-period which experienced a low economic growth, high inflation and poor governance, momentum returns are negative for most of the portfolios. Analysis also shows that momentum portfolios continue earning positive returns beyond the holding period indicating that the returns are not caused by temporary over- or under-reaction of investors in the market and they must be related to some systematic risk factors. However, the study does not find any evidence of relationship between beta and size factors and the momentum returns