When asked by Defence Attorney Patrick W Belgan if he was still proud of the Mumbai attacks that killed more than 160 people including American nationals, Headley said, "No".
Headley was testifying in a court here on the fourth-day of the trial of Pakistani-Canadian Tawahhur Rana, another co-accused in the case. The statements formed part of the testimony of Headley, who has pleaded guilty.
Headley, who carried our extensive surveillance of the strike site for months before the attacks by Lashkar-e-Taiba (LeT) said he was "proud" of what he did at the time of the attacks.
People, who knew that he was involved in the planning stage of the strike sent him congratulatory messages after the Mumbai mayhem, including Pasha, his wife and Sajid Mir, Headley said.
Questioning of Headley, 50, would resume on Tuesday.
Earlier, responding to questions from Belgan, Headley said he feels that the Mumbai attacks were in retaliation of the alleged killing of people by the Indian Army in Kashmir.
According to court documents, Headley wanted to go to Kashmir after he received training from LeT, however, his handlers decided to keep him for other operations like 26/11.
"So it is OK to kill people in Mumbai," he argued.