Bentley, a 76-year-old grandfather of eight, inadvertently texted his wife of 50 years, Dianne, with a message meant for his mistress, former adviser Rebekah Caldwell Mason.
Intentional violations of the Alabama Ethics Act and Fair Campaign Practices Act are Class B felonies, punishable by a prison sentence of between two and 20 years for each violation.
Bentley pleaded guilty to two campaign violations - converting campaign contributions for personal gain and failing to report campaign contributions - and was booked briefly into jail around 4 p.m., before being released on $600 bond.
Bentley, 74, has battled impeachment efforts over the previous year.
The Alabama Ethics Commission also recently issued four findings of probable cause that Bentley violated state campaign finance law and the ethics law.
Bentley's wife, Dianne Bentley, discovered the texts between Mason and her husband and she is the one who submitted them to the committee. The report authors also specified that they considered Bentley's attempts to obstruct the investigation by withholding messages as an "independent ground for impeachment".
Bentley tapped state Attorney General Luther Strange, who was reportedly investigating Bentley, to fill Sessions' seat.
A report released by a state ethics panel accused Bentley of ordering law enforcement officers to track down copies of an embarrassing recording that suggested he had had an affair with Mason.
But over the past few days, the political and legal tides finally turned overwhelmingly against Bentley, and reluctant Republicans have had no choice but to break with the governor.
"He would have done anything for the Governor, including taking a bullet".
In court, Bentley's lawyers tried to delay impeachment with fairness claims.
Bentley acknowledged his mistakes, but has denied doing anything illegal.
"There have been times when I have let you and our people down, and I'm sorry about that", he said. On Friday, facing public criticism and pressure from his own party, he vowed to remain in office. He has repeatedly said he won't quit, saying there's no reason.
The agreement comes on the day of impeachment hearings were set to begin, allowing Bentley to avoid the public spectacle. The first hints of scandal came more than a year ago, when Bentley fired Spencer Collier, the head of the Alabama Law Enforcement Agency.
"There are some significant questions regarding Gov. Bentley's candor in investigative efforts", said Jack Sharman, Special Counsel for the House Judiciary Committee.
In other texts between the governor and Mrs Mason, one from her phone said: "You handsome, wonderful, amazing, delicious, funny, sweet man".
Then-Lt. Governor Kay Ivey and Gov. Robert Bentley in 2016. He stood up and said "yes, sir" in a gravelly voice as the judge read out the charges he was pleading guilty to.
Alabama's governor has quit over his relationship with an aide in one of the state's biggest political scandals. These former allies include "House Speaker Mac McCutcheon and Senate President Pro Tem Del Marsh".
Legislative leaders had been carefully noncommittal about impeachment since House members first pushed a resolution through past year, but the Ethics Commission report, combined with the impeachment proceeding, pushed Senate President Pro Tem Del Marsh, R-Anniston and House Speaker Mac McCutcheon, R-Monrovia, both called for Bentley's resignation last week.