The Wednesday night arrests for possession of a controlled substance occurred in West Hollywood during a traffic stop, Los Angeles sheriff's deputy Mark Pope told The Associated Press.
"Deputies smelled a strong odor of marijuana emitting from the vehicle," the department said. "A narcotics investigation ensued" that resulted in the arrests.
The department's media office said it didn't yet have details on which specific drug the possession charge concerned.
The arrests reflect that last week of socialite Paris Hilton, whose is being investigated for felony cocaine possession after a motorcycle officer smelled pot wafting from her car.
The Atlanta-based T.I., 29, whose real name is Clifford Harris Jr., and Cottle, a 36-year-old singer who sang with the 1990s group Xscape and has recently been the star of the BET reality series "The Tiny & Toya Show," were booked at the West Hollywood sheriff's station. Bail was set at $10,000 each.
Pope said Thursday that he didn't know if they were still being held.
T.I.'s publicist declined to comment.
T.I., the multiplatinum hitmaker who has a key role in the current top box office movie "Takers," served seven months in an Arkansas federal prison and three months in a Georgia halfway house on federal weapons charges and was released in March. He is on three years' probation.
Since that case, T.I., who had spent time behind bars for drug offenses before, vowed to live a better life. He spoke to kids about the dangers of drugs and guns, and former United Nations Ambassador Andrew Young was one of his supporters. As he prepared for his most recent sentence, he starred in the MTV reality show "T.I.'s Road to Redemption: 45 Days to Go."
The father of five married Cottle in late July. "Takers," a shoot 'em up about an armored truck robbery that goes bad, was released last week and topped the box-office chart.
In a recent interview with The Associated Press, T.I. talked about living a more positive life.
"Right now, it's all about moving forward and just acknowledging the blessing that are here today. ... Just moving past the regrets of yesterday - the things that could've been done better," T.I. said in a July interview.
T.I., who is known as the "King of the South," has emerged one of music's most profitable stars over the last few years. He is working on a new album, King Uncaged, which may be released this year.