The singer, who has had two long-running residencies in Vegas, the first in 2003, told the crowd proceeds from the night would go to the victims of Sunday's shooting at the Route 91 Harvest Festival and their families.
Dion said she ultimately decided to go on with her performances "to show love and support for those who are affected."
"On Sunday, we lost too many beautiful, innocent souls and so many are still suffering. But tonight, we are going to let these families know that we are supporting them and that we will help them through their tragic loss," she said. "They are going to need a lot of love, a ton of emotional support, as well as a great deal of financial aid."
Her announcement that proceeds would be donated drew more than 30 seconds of applause from the crowd.
Dion also dedicate the show to the victims, their families, first responders, and doctors and nurses "who are working around the clock to save lives."
"I want you to know that you have made the right choice in being here tonight," she said.
Read More: Celine Dion donates concert proceeds to Vegas shooting victims