The debate in Reno takes place tonight at 8 p.m. and will be broadcast on PBS stations statewide.
Heller was appointed last year by Gov. Brian Sandoval to fill the vacancy left when John Ensign resigned.
Berkley is a seven-term congresswoman from Las Vegas.
She is under investigation by the House Ethics Committee for not disclosing her husband's ties to a Las Vegas kidney center when voting on policies that benefited her husband's medical practice.
Heller's campaign has focused on that investigation and Berkley's support of the federal health care overhaul.
Berkley has tried to paint Heller as being out of touch with the middle class.