The suit relates to a dispute over a coal supply contract.
The jury issued its verdict on Friday afternoon following a five-week trial in Grundy.
The owner of Harman, Hugh Caperton, said his companies were financially damaged when Massey slashed the amount of coal it had agreed to buy. Harman Mining ceased operations in 1998.
A Buchanan County jury awarded $4 million in damages to Harman Mining and two related companies. The jury also awarded $1 million to Caperton for personal financial damages, media outlets reported.
Alpha Natural Resources bought Massey in 2011 and assumed many of its liabilities, including the Caperton lawsuit.
"We're not only pleased with the outcome of this case, but convinced it reflects the factual evidence presented to the jury," Alpha spokesman Ted Pile told The Wall Street Journal.
Caperton's lawyer, Bruce Stanley, told the Charleston Gazette he was pleased that the jury had found Massey liable for putting Harman out of business and for the injuries it caused Caperton.
But he indicated that they would likely appeal the jury award's amount. Caperton had sought $90 million in compensatory damages.
“We are not finished," he said.
"We will take a look at all our available options and do whatever is within our power to hold Massey accountable for the full extent of the injuries they caused."