Victor Conte, the head of the San Francisco-area BALCO labs, is accused of distributing steroids in a scandal that has damaged the reputations of top athletes in baseball, American football and track and field.
He exasperated his former attorney Robert Holley by confessing in an article and television interview in December that he did distribute steroids as charged.
"Mr Conte and I have a conflict of interest and that is why I am getting off the case," Holley told a judge on Friday as Conte presented his new legal team.
The change came ahead of a scheduled March 16 court hearing to review whether law enforcement authorities acted improperly in searching BALCO's offices in 2003.
That hearing will now be delayed.
"Mr Conte wanted to make a fresh start," said Conte's new attorney Mary McNamara, who specialises in white collar criminal law.
"We intend to vigorously defend Mr Conte."