Four-time Olympic gold medallist Laura Kenny, 24, revealed the news with a post on Instagram of two adult bikes lined up alongside a child's bike.
Husband Jason added his own post on Twitter, while Great Britain team-mate Dani King tweeted "best news ever".
Agent Luke Lloyd-Davies said the couple and their families are "absolutely thrilled and delighted with the news".
"They very much appreciate all the kind wishes and messages of support that they have received already," he added.
The couple, who married in September in a private ceremony, went public with the news following their 12-week scan.
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Jason, 28, has won six track cycling Olympic gold medals, including three at last summer's Games in Rio.
Laura pulled out of last month's National Track Championships after injuring a hamstring, but said at the time she hoped to be fit for April's World Championships in Hong Kong
Britain's Olympic champions Jason and Laura Kenny are expecting their first child, the couple's agent confirmed.