"The whole thing has been very painful for me", the news anchor told People on Saturday.
Couric called the allegations made against her former co-host "disturbing, distressing and disorienting" and said such behavior is "completely unacceptable".
Couric added that Lauer's conduct to her was always professional, and that he was like a brother.
'I had no idea this was going on during my tenure or after I left.
'Matt was a kind and generous colleague who treated me with respect.
The veteran news anchor told People she is still struggling to process the allegations.
"There are no words to express my sorrow and regret for the pain I have caused others by words and actions", Lauer said in a statement released by NBC.
Couric also praised Today's Savannah Guthrie and Hoda Kotb, who has taken Lauer's place on the show, for how they have dealt with the situation. She added that "It's still very upsetting", and that she "really admire [s] the way Savannah [Guthrie] and Hoda [Kotb] and the entire Today show staff have handled a very hard situation". At the time, NBC said his behavior "may not have been an isolated incident".
Until her People interview, Couric had only commented once on the Lauer scandal, last month on Instagram in response to a user asking her why she had not spoken up. "I really admire the way Savannah (Guthrie) and Hoda (Kotb) and the entire "Today" show staff have handled a very hard situation". In December, Couric said the claims were "upsetting" but that she would only speak when she was "ready". "As I am writing this I realize the depth of the damage and disappointment I have left behind at home and at NBC", he said.