The union said it will request the National Labor Relations Board to hold a hearing to determine if the results should be set aside, accusing Amazon of "creating an atmosphere of confusion, coercion and/or fear of reprisals" and interfering with the employees’ freedom of choice.
Employees at Amazon.com Inc.’s Bessemer, Alabama, facility opposed forming a union by a 1,798 to 738 margin.
About 55% of the approximately 5,800 workers who were eligible to vote participated and less than 16% of employees backed unionization.
If approved, the warehouse would have become the first Amazon location to unionize.
"We won’t let Amazon’s lies, deception and illegal activities go unchallenged," said Stuart Appelbaum, president of the Retail, Wholesale and Department Store Union. "We demand a comprehensive investigation over Amazon's behavior in corrupting this election."
He accused Amazon of requiring employees to attend lectures that contained "mistruths and lies" aimed at persuading them to oppose forming a union and with flooding the internet and airwaves with ads that spread misinformation.
He also claimed Amazon went against an NLRB ruling and worked with the U.S. Postal Service to install a drop box on warehouse property.
Amazon said in a statement that it’s "not true" that it intimated employees and that workers heard far more anti-Amazon messaging.
The company says now that the election is over it welcomes the opportunity to "sit down and share ideas" with any lawmaker who wants to discuss $15 minimum wage, health care and other benefits.