The 39-year-old wrote, "My thoughts are with all the families in QLD dealing with the terrible floods. 8 confirmed dead, many missing & more flooding predicted."
At least 72 people are missing after a wall of water, described as an "instant tsunami", swept through Toowoomba and the surrounding region on Monday night.
Eight people, including four children, are confirmed dead.
More deaths are expected and the city of Brisbane is preparing itself to be hit by floodwater later today.
Dannii lives in Melbourne, Victoria, well away from the flooded areas, with boyfriend Kris Smith and their baby son, Ethan.