- AbstractThe main aims of this study to investigate the impact of the determinant of portfolio return performance during and post finical market crisis based on the most active firms listed on Amman Stock Exchange (ASE) for the period from 2008 to 2012 has been studied. In this study,using the framework of the Capital Assets Pricing Model (CAPM) as considered to be a centrepiece inoptimal portfolio determinants. An important contribution of this framework is that it allows toderive optimal portfolio implications for economies in which the degree of correlation acrossdifferent finical sectors. The test data set is the monthly prices based on 59 samples of the mostactive companies. This empirical study proposed that this is not a normal cyclical crisis ofcapitalism but a global crisis, which requires a change in the management policy to be tackled withnew regulatory frameworks for financial institutions in order to stimulate economic activities. Theresults show that there is a difference finding during these two periods where risk is negative andsignificant during finical market crisis period (2008- 2009) but positive and significant after thefinical market crisis period (2010-2012). Further resultsshow that when the return on the otherfactors is inserted in the model, this relation remains significant during and post finical marketcrisis for asset correlation and investment risk. Furthermore, paper of the proposed model in otheremerging countries could be performed in order to raise further explanation of the model and to reveal more generalised findings.