The win came just five days before her 29th birthday on Saturday.
McFadden, an Atholton graduate, is coming off an injury plagued 2017 where she was hospitalized early in the year with life-threatening blood clots and finished fourth in Boston. She later returned to win the Chicago Marathon in October and finish second in the New York City Marathon.
Her win today was the fifth Boston Marathon title and 22nd women’s major marathon of her career. Major marathons are Tokyo, Boston, London, Berlin, Chicago and New York City.
McFadden's unofficial finishing time 2:04:39 was the slowest in 30 years, but that can be attributed to the cold and rainy conditions. She won four straight Boston races from 2013 to 2016.
McFadden said she wore two jackets, with plastic bags between layers to stay dry, and hand warmers against her chest. The wet roads made it treacherous to turn and impossible to stop.
“I could start to feel my arms getting heavy just from all the rain soaking in,” she said. “You can't put your brakes on right away, so you had to be tedious on the turns. I couldn't even see because the wind was so strong.”
The other winners in the 122nd Boston Marathon:
>>Women: Desiree Linden splashed her way through icy rain and a near-gale headwind to become the first American woman to win the race since 1985.
The two-time Olympian and 2011 Boston runner-up pulled away at the end of Heartbreak Hill and ran alone through Brookline to finish in an unofficial time of 2 hours, 39 minutes, 54 seconds. That's the slowest time for a women's winner since 1978.
>>Men: Japanese runner Yuki Kawauchi surged late to win men's Boston Marathon in an unofficial time of 2 hours, 15 minutes and 58 seconds.
Kawauchi is the first Japanese man to win the Boston Marathon since 1987.
He overtook Kenyan runner Geoffrey Kirui in the last few miles to win his first Abbott World Marathon major title.
>>Men wheelchair: Marcel Hug won the men's wheelchair race for a fourth consecutive year.
The 32-year-old from Switzerland took a commanding lead in the second half of the race and held it to finish in an unofficial time of 1 hour, 46 minutes, 26 seconds.
It was the slowest winning time in the men's wheelchair race in 31 years.