The debts of President-elect Donald Trump and his businesses are scattered across Wall Street banks, mutual funds and other financial institutions, broadening the tangle of interests that pose potential conflicts for the incoming president’s administration.

Hundreds of millions of dollars of debt attached to Mr. Trump’s properties, some of them backed by Mr. Trump’s personal guarantee, were packaged into securities and sold to investors over the past five years, according to a Wall Street Journal analysis of legal and property...