Trump's 2016 federal disclosure forms, filed in May, show he owned between $15,000 and $50,000 in stock in Texas-based Energy Transfer Partners.
That's down from between $500,000 and $1 million a year earlier.
Trump's form also shows he holds between $100,000 and $250,000 in Phillips 66 stock, which has a one-quarter share of Dakota Access.
Campaign contribution disclosures show that Energy Transfer Partners CEO Kelcy Warren donated $3,000 to Trump's campaign, plus $100,000 to a committee supporting Trump's candidacy, as well as $66,800 to the Republican National Committee.
Trump's stake and the donations were first reported Wednesday by The Guardian.