Schoolteacher Megan Pinion received the offending cups of coffee at the Mall of Louisiana, in Baton Rouge, La., where an allegedly devil-worshipping barista served her a pair of coffees decorated with a pentagram, the sigil of the Satanic goat god Baphomet, and the number 666, the Biblical number of the beast.
Pinion, a Catholic, took to Starbucks's Facebook page to register her displeasure.
"I am in no way judging [the barista's] beliefs or dis-meriting his beautiful artwork," she wrote alongside an image of the two coffees. "I am however judging his lack of professionalism and respect for others."
Through social media, Starbucks has apologized to Pinion for the barista's behavior.
"This is obviously not the type of experience we want to provide any of our customers, and is not representative of the customer service our partners provide to millions of customers every day," Starbucks spokesman Tom Kuhn added in a statement to The Huffington Post.
The coffee chain did not address its relationship with Baphomet.