Instead, Bears security personnel escorted Brown -- who's currently a member of the New Orleans Saints -- out of the building.
Brown seemed surprised when he tweeted about the incident on his Twitter page @alexbrown96. But a Bears official said NFL rules forbid players under contract to visit another team's facilities.
"We love Alex Brown," the team official said. "He's got friends throughout Halas Hall, but league rules don't allow us to host a player under contract at our facility.
"He's one of the great guys. He's one of the top-notch guys who have come through in a long time."
Brown didn't return calls or text messages seeking comment.
Released by the Bears after producing a six-sack season in 2009, Brown signed a two-year contract with the Saints in April worth $6 million. He appears set to break into the starting lineup due to the recent release of his college teammate at Florida, Bobby McCray.
Brown started in 107 of 127 career games with the Bears, producing 43.5 sacks, in addition to forcing 16 fumbles.
Michael C. Wright covers the Bears for ESPNChicago.com.