The mother-of-three, who regularly provides sports bulletins for Sky, took to Twitter to tell her more than 30,000 followers of the diagnosis - which was made a day before Christmas.
The long-serving presenter, a former British rhythmic gymnastics champion, wrote: "Been neglecting my twitter had a bit of a wobbly time of it - diagnosed with Breast Cancer on Xmas Eve - all positive thoughts welcome !! Thanks everyone for your amazing tweets - made me feel all emotional - not good when you're about to do eyeliner ! Xx"
Celebrity friends and colleagues have tweeted their support for Beltrao, who represented Great Britain at the Los Angeles Olympics in 1984.
Fellow Sky stalwart Kay Burley wrote: "Just been chatting with @SkyJacquie. Pls send your love."