Injured in the Boston Marathon bombing last year, Costello underwent multiple surgeries to treat burns and shrapnel injuries, then was moved to Spaulding Rehabilitation Hospital. There, he met D'Agostino, a traveling nurse working on a six-week stint at the rehab center.
In December, they got engaged on a trip to France. On Saturday, they were wed.
"One thing that she hates that I always say is I'm actually glad I got blown up,'' Costello said of their unlikely fairytale, after the engagement. "I wish everyone else didn't have to, but I don't think I would have ever met her if I didn't, so I'm pretty happy."
Nearly everything for the nuptials was donated by local businesses: the Hyatt Regency in Boston donated the space, and wedding planner Rachel Gross helped create a "nautical wedding, but without the literal nautical elements." Bella Sera Bridal boutique in Danvers, Mass., donated D'Agostino's Swarovski-crystal encrusted Allure Couture gown, and Blooms of Hope in Belmont provided the white and blue hydrangeas that decorated the space and made up the bride's bouquet.
Prudente Photography, Montilio's Baking Company, New England Country Rentals, Lynn Graham Designs, Gooseflesh Press and Italian singer Antonio Cassisi pitched in, while I Do Films flew in from Chicago on their own dime.
Their first dance was to John Legend's "All of Me," first with the crowd joining them to an upbeat mix of the song, then as a couple to the ballad version.
"It was such a true representation of their character, their style, and their love," said Gross. "Everyone was soaring, soaring."
D'Agostino and Costello said they would make a donation to the Semper Fi Foundation to help provide the means for a military couple to have a wedding.
"They just want to give someone a special moment like we've given them," said Gross.
The happy couple is now in Hawaii on their honeymoon.