Adidas issued its mea culpa, saying: "We are incredibly sorry".
Three people were killed and more than 260 wounded when two bombs exploded near the finish line.
The choice of words jarred as memories remain fresh of the 2013 deadly bombing of the event in the MA city.
The email in question arrived bearing the subject line: "Congrats, you survived the Boston Marathon!"More news: Zimmermann sharp as Tigers beat Red Sox 4-1
"We are incredibly sorry", the company said in an e-mailed statement.
This has been a banner month for brands falling on their faces on social media, thanks to Kendall Jenner's Pepsi ad, the United Airlines debacle and Cosmopolitan calling cancer a weight loss trend. "We deeply apologize for our mistake", the company's statement read. Every year we're reminded of the hope and resiliency of the running community at this event.
"Poor choice of words for the Boston marathon", one Twitter user said.
Others expressed a similar sentiment.
The email also included the phrase, "You're Boston Strong, what's next?"