The photographs, one of which depicts the former Aussie fast bowler sitting and smiling with a rifle in front of a dead elephant, sparked outrage on Twitter on Saturday afternoon.
In a statement, McGrath said he regretted taking part in the 2008 hunt. In the same year, he lost first wife Jane to breast cancer.
"It was an extremely difficult time in my life and looking back I deeply regret being involved," he said.
The photos, originally posted on the website of Chipitani Safari co, also show McGrath posing with a dead buffalo, dead hyenas and a number of animal bones.
The pictures no longer appear on the website of the company.