At 10:17am, the KSE-100 index of the Pakistan Stock Exchange traded 1.96pc lower at 37,484.18 points.
"It's due to Brexit. It's the volatility in global markets," said Saad Hashmey, chief economist and director of research for Topline Securities.
Traders said banking and oil stocks were leading the decline.
Britain has voted to leave the European Union, results from Thursday's landmark referendum showed, an outcome that sets the country on an uncertain path and deals the largest setback to European efforts to forge greater unity since World War Two.
World financial markets dived as nearly complete results showed a 51.8/48.2 per cent split for leaving.
Sterling suffered its biggest one-day fall of more than 10pc against the dollar, hitting a 31-year low on market fears the decision will hit investment in the world's 5th largest economy.
The euro slumped more than 3pc against the dollar on concerns a Brexit vote will do wider economic and political damage to what will become a 27-member union. Investors poured into safe-haven assets including gold, and the yen surged. European shares were on course to open 6 to 7.5pc lower.