According to Us magazine, the pair decided to split after attending the Lance Armstrong Livestrong Summit in Columbus last weekend.
The pair have been dating for the past three months and have been spotted together at events in Austin, New York and Los Angeles.
A source commented: "There was no drama or ugliness. They just decided to end things. There is no hatred, just sadness."
Armstrong recently met Hudson's mum Goldie Hawn, while the actress's four-year-old son Ryder enjoyed Father's Day with the cyclist.