The 22-year-old singer is said to have split from the 18-year-old son of Robert F Kennedy Jr and the late Mary Kennedy after a couple of months of dating, reported Us magazine.
"They quietly parted ways a while ago. It was just a distance thing. No hard feelings. They're fine," a source said.
The split was triggered by her busy schedule in promoting her latest album, 'Red'.
"It's been over a month since they've even seen each other. With her promotion for Red, she has no time off until the end of the year," the source added.
Swift and Kennedy were first seen in July holding hands at his family's compound in Massachusetts. She brought him to meet her parents in Nashville, Tennessee in August and they visited his mom's grave in Cape God in the same month.
The relationship was heading into something serious as the Kennedy family gave approval.
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However, in a recent interview, Swift said that she hardly knows how to maintain love.
"I don't know how to have a normal relationship because I try to act normal and love from a normal place and live a normal life, but there is sort of an abnormal magnifying glass, like telescope lens, on everything that happens between me and anybody else," she said.
Swift previously dated Joe Jonas, Taylor Lautner, Jake Gyllenhaal, John Mayer and Cory Monteith.