"We are so sad about the loss of life and injury that occurred on a day that carried so much promise, but turned so wicked so quickly," the actor said in a statement Monday.
"We hope to return to Alberta in the future to help with the healing."
Costner and his band, Modern West, were the next band scheduled to take the stage when a terrifying windstorm swept through the site of the Big Valley Jamboree.
The strong blast of wind collapsed the main stage so quickly that organizers did not have time to warn thousands of fans crowded around it.
Concertgoer Donna Moore, 35, was killed when a giant speaker fell on her and two others suffered critical injuries. Dozens of people were treated for non-life threatening wounds.
Costner was on the stage when it collapsed and was caught under some debris but was not injured. However, two of his crew members were hurt, said his publicist, Arnold Robinson.
"My understanding is that they sustained cuts and bruising," Robinson said. "Kevin went to the hospital with (them), they were treated and released, and he did visit with others that were injured while there."
Robinson said Costner is willing to do more to help.
"In the event that there is any type of benefit to support the victims, he would hope to be a part of it," Robinson said.
Country singer Billy Currington was playing his last song at the Jamboree when the stage collapsed on top of him, leaving the country star with a minor concussion.
His bassist, Alex Stevens, was pinned under the wreckage for 30 minutes while crews worked to free him. Stevens underwent surgery on his left arm and is recovering in Nashville.
The stage collapse is under investigation by Alberta Occupational Health and Safety, but a spokeswoman said Monday it's too early to know what happened.