City officials say William Mason was responding to an emergency water leak Tuesday in a Yuma subdivision.
While he was working, the cactus fell on him.
Other members in his work crew were able to free him and call 911.
The city says Mason suffered multiple injuries to his back and legs and remains hospitalized at Yuma Regional Medical Center.
Saguaro cactuses can weigh anywhere from hundreds of pounds to more than several thousand pounds, depending on how much water they're holding.