He was arrested shortly after midnight in Carmel, a suburb just north of Indianapolis, on the initial charge of operating a vehicle while intoxicated. Carmel Police said the 36-year-old Mathis was driving the wrong way on a one-way street and did not signal a turn.
Mathis' blood alcohol content level at the time of his arrest was .052, which is below Indiana's legal limit of .08. But Carmel Police Sgt. D.J. Schoeff told ESPN that it was determined that Mathis was too impaired to drive after a number of field sobriety tests.
"We are aware of the incident involving Robert Mathis last night," the Colts said in a statement Tuesday. "We are in the process of gathering more information and have no further comment at this time."
The Colts hired Mathis last month to be the team's pass-rush consultant.
Mathis spent his entire 14-year NFL playing career with the Colts. He is the franchise leader in sacks (123) and has an NFL-record 40 career strip sacks. His best season was in 2013, when he had 19 1/2 sacks.
He was suspended for four games in 2014 for using performance-enhancing drugs. He eventually missed the entire season after tearing his Achilles.
The Associated Press contributed to this report.