Wallace said in an interview with TMZ Sports regarding Randolph, "I know for a fact, he ain't no dope dealer."
Randolph was arrested last week in Los Angeles and charged with felony marijuana possession with intent to sell due to allegedly carrying two pounds of marijuana, per TMZ Sports.
Randolph made $20,000 bail and is now awaiting further legal proceedings.
Wallace called for Z-Bo to keep his head up, but suggested NBA discipline could be forthcoming if he is found guilty.
Sheed and Randolph were frontcourt partners in Portland from 2001-02 until 2003-04 when Wallace was traded to the Atlanta Hawks and then the Detroit Pistons just days later.
The 36-year-old Randolph spent the past eight seasons with the Memphis Grizzlies. He made two All-Star Games and developed into one of the most beloved and successful players in franchise history.
He will begin a new chapter in his career this season, though, after signing a two-year contract with the Sacramento Kings.