McCullum agreed to a six-year contract at undisclosed terms. He replaces Seth Greenberg, who stepped down after seven seasons to become coach at Virginia Tech.
The Tampa Tribune reported that McCullum was given a six-year, $1.62 million contract.
Western Michigan was 44-45 in three seasons under McCullum, including a 20-11 record this past season and a berth in the National Invitation Tournament.
"The success he has enjoyed at each step of his career and the remarkable job he has done at Western Michigan makes him the ideal person to lead our program to new standards of excellence," said USF Director of Athletics Lee Roy Selmon. "Coach McCullum will lead a USF basketball program that wins with integrity."
"As a basketball player, but more importantly, as a person, you get on the road to success with your attitude and the way you approach things," McCullum said.
He already has met with this year's holdover players.
"I have high standards and expectations in all areas of their lives," McCullum said. "I wasn't preaching to them or trying to intimidate them, but I wanted to make it clear that we need to do things a certain way."
Before arriving at Western Michigan, McCullum was an assistant at Illinois and Florida. At Florida, he was recognized as a top recruiter, and helped mold a program that reached the Final Four in 1994.
In seven seasons at South Florida, Greenberg's teams posted a 108-100 record, including a 15-14 mark this year. He twice took the Bulls to the NIT, but failed to make the NCAA Tournament.