The couple, who have been dating for four years, announced their happy news via Twitter on Thursday evening (13 August).
Janette proudly revealed that Aljaz had popped the question. She gushed: "I said 'YES'!" with a heart emoji.
In the photo, Janette shows off her ring, while her and Aljaz hold up a celebratory 'congratulations' plate.
Fellow professional dancer Kevin Clifton, who married Karen Hauer in July, tweeted: "Congrats to 2 of our best mates. Beautiful couple @AljazSkorjanec @JManrara."
Aljaz and Janette joined Strictly as professional dancers in 2013 and will be back when the new series returns this September.
Try Reveal's digital edition on iPhone & iPad. Subscribe now & never miss an issue!