Stallworth, 28, was sentenced on Tuesday to 30 days in jail for the car crash that killed a pedestrian on Miami Beach.
"The conduct reflected in your guilty plea resulted in the tragic loss of life and was inexcusable," Goodell wrote in a letter to Stallworth.
"While the criminal justice system has determined the legal consequences of this incident, it is my responsibility as NFL Commissioner to determine appropriate league discipline for your actions, which have caused irreparable harm to the victim and his family, your club, your fellow players and the NFL."
Tests showed Stallworth had a blood alcohol level of 0.126, well above Florida's legal limit of 0.08, when he hit and killed 59-year-old construction worker Mario Reyes on March 14, court documents said.
Stallworth had been drinking at a Miami Beach club before crashing his black Bentley into Reyes, who was walking across the MacArthur Causeway after his shift as a crane operator.
"There is no reasonable dispute that your continued eligibility for participation at this time would undermine the integrity of and public confidence in our league," wrote Goodell.
"Accordingly, I have decided to suspend you indefinitely, effective immediately."
Stallworth, a seven-year NFL veteran, signed a seven-year, $35 million deal with the Browns last year but played in only 11 games due to injuries.
His jail term will be followed by two years of house arrest and eight years' probation, and his driver's license has been suspended for life.
Stallworth was also ordered to pay $10,000 in fines and perform 1,000 hours of community service.
