Blankenship was acquitted on two other felony charges, according to CNN affiliate WCHS
: securities fraud and making false statements to the U.S. Securities and Exchange Commission.
The former CEO ran the West Virginia mine that exploded in 2010, in what was one of the worst U.S. mine disasters in decades.
Sentencing is set for March. Blankenship could face up to a year in federal prison.
"This is a landmark day for the safety of coal miners. Really it's a landmark day for all working men and women," Booth Goodwin, U.S. Attorney for the Southern District of West Virginia, told reporters. "The CEO and chairman of one of America's largest coal companies now stands convicted of willful violations of the laws that are designed to keep coal miners safe."
He said that it was his hope the verdict would make a difference throughout the country.
"To go from boardroom to the prospect of incarceration sends a powerful message to executives who would ignore the safety of their workers. It doesn't matter who you are, how rich you are, how powerful you are, if you violate the laws and gamble with the lives of your workers, you will be held accountable," Goodwin said.
Blankenship's attorney told reporters his team was disappointed by the jury's decision, but he believes the conviction will be overturned on appeal.
"We wanted to be acquitted on all counts, but the fact the jury acquitted him on all felonies and convicted only on the misdemeanor is some consolation," WCHS reported attorney Bill Taylor as saying.
Massey was the fourth-largest coal producer in the United States and the largest mine operator in Appalachia at the time of the Upper Big Branch explosion, which killed 29 workers.
But it had racked up an extensive list of violations before the disaster, and a 2011 report by the U.S. Mine Safety and Health Administration found that Massey had a history of "systematic, intentional and aggressive efforts" to evade safety regulations.
The company kept two sets of books to mislead miners and inspectors, tipped off crews before surprise inspections and intimidated workers to prevent them from reporting violations, the report found.
Massey was bought by another company, Alpha Natural Resources, after the disaster. In December 2011, it settled with the Justice Department for a record $209 million in fines, penalties and compensation for families of the men killed at Upper Big Branch.