The hedge-fund manager's former deputy, Stanley Druckenmiller, however, foresaw the rally and gained a sizable profit, the Journal reported, citing people close to the matter.
The sources told the Journal Soros was cautious about the market going into the election and became bearish after Trump won.
Stocks and Treasury yields jumped in the wake of Trump's victory, amid the prospects of looser regulations in certain sectors, lower tax rates, and fiscal stimulus.
Soros' hedge fund, Soros Fund Management, manages about $30 billion for Soros and his family. Soros was a supporter of Hillary Clinton's campaign.