Employees at Ellsworth-based Maine Coast Memorial Hospital voted to join the Maine Nurses Association, which is part of National Nurses United.
The vote, conducted via a secret ballot election this week, covers medical laboratory technicians, CT/radiology technologists, respiratory therapists and licensed practical nurses.
In a news release, the union said issues such as "safe staffing, retirement security, adequate equipment, and other patient and economic protections" prompted the vote.
Hospital leadership expressed disappointment with the vote.
"While we are disappointed with the results of the election and prefer to work with our employees directly, we remain committed to supporting this group and all of our employees," spokesperson Kelley Anne Columber said in a statement to the Bangor Daily News.
Before this week's vote, more than 100 nurses, medical technologists and social workers at MCMH were members of MSNA.