The study has focused on the foreign portfolio investment (FPI) in Pakistan Stock Exchange (PSX). Mixed-method approach is applied to analyse quantitative and qualitative data. The study analyses three types of data, thus it presents three different analysis procedures. Quarterly data from secondary sources (2007Q3 to 2017Q2) of ten consecutive years, primary data collected through questionnaire and qualitative data collected through interviews have been analysed. Firstly, drivers of FPI are identified and explored through secondary data. Two different sets of variables (macroeconomic variables and stock market indicators) are explored. Macroeconomic variables include economic growth activity, interest rates, exchange rate risk, inflation rate, country risk and foreign direct investment (FDI). The set of stock market indicators include stock market size/capitalization, stock market returns, stock market risk, stock market liquidity and stock market index. The relationship of both sets of variables with the dependent variable has been explored. Correlation is checked along with Co-integration analysis. Co-integration is carried out for checking the long-term relationship between the selected variables. After establishing long-term relationship, short-term relationship has been explored through Vector Error Correction Model (VECM). Furthermore, magnitude of these relationships has been checked by doing the multiple regression analysis through Ordinary Least Square (OLS) method. After secondary data analysis, the influence of FPI flows on the investment decisions of domestic institutional investors has been checked by analyzing primary data collected through questionnaire-based survey from domestic institutional investors listed at PSX. The questionnaire comprises of thirty questions, covering three behavioural factors; overconfidence, conservatism and herding effect in the context of FPI. Six separate questions have been asked in order to triangulate the results of secondary data analysis. The responses have almost supported the results of the secondary data analysis. For further thorough analysis, interviews from ten domestic institutional investors have also been conducted. The respondents were asked that whether FPI flows really influence the investors’ investment behaviour and secondly, suggestions regarding investment decisions have also been sought from them. Almost, all of the interviewees responded cooperatively and suggested that government should take steps in order to provide safety to foreign investors and protect the small domestic investors as well, especially, in crisis situations. Thus, this study has been carried out about the foreign investment in Pakistan by applying mix-method approach with quantitative and qualitative data analysis. The study has clear policy implications for the policy makers and the stock market stake holders.