Johnson already is suspended for the first eight games of the 2007 NFL season after violating probation on a gun violation.
Police in the Phoenix suburb of Gilbert said Johnson was stopped for driving 40 mph in a 25 mph zone at 3:30 a.m. Friday and the officer made observations that led him to believe Johnson was impaired.
Sgt. Andrew Duncan, a police spokesman, said Johnson was arrested for "DUI Impaired to the Slightest Degree" but was released without being booked or charged.
Duncan said Johnson was taken to the Gilbert police station, where officials drew blood for a blood-alcohol content test before his release. He described Johnson as "very cooperative."
The officer had probable cause to make an arrest, Duncan said. Test results aren't expected for up to two weeks, and they would be sent to Gilbert town prosecutors for consideration of any charges.
"We are aware Tank was pulled over early Friday morning in Arizona," the Chicago Bears said in a statement. "We are currently gathering facts regarding the incident. We will withhold further comment until we have more information."
It was not immediately clear why Johnson was in Arizona although he attended high school in the Phoenix suburb of Tempe.
Earlier this month, NFL commissioner Roger Goodell suspended Johnson for half the regular season for violating the league's toughened personal conduct policy.