"It is with deep regret that, after several emotional and very personal discussions with his family, his doctors and my client himself, I have made the decision to terminate my professional relationship with Johnny Manziel," agent Erik Burkhardt said in a statement.
"Though I will remain a friend and Johnny supporter, and he knows I have worked tirelessly to arrange a number of professional options for him to continue to pursue, it has become painfully obvious that his future rests solely in his own hands. His family and I have gone to great lengths to outline the steps we feel he must take to get his life in order. Accountability is the foundation of any relationship, and without it, the function of my work is counterproductive.
"I truly wish the best for Johnny and sincerely hope he can, and will, find the kind of peace and happiness he deserves."
The move comes three days after the Browns released a statement saying they would address Manziel's status "when permitted by league rules" and less than a week after Manziel's latest incident, in which he was accused of striking his ex-girlfriend during an altercation in Dallas. Police in Dallas and Fort Worth, Texas, both said Manziel would not be charged and that the cases were closed.
A source told ESPN's Pat McManamon earlier this week that the Browns plan to release Manziel in March.
Last month, LeBron James also dropped Manziel as a client from James' LRMR marketing firm.
Burkhardt negotiated Manziel's four-year rookie contract worth $7.07 million in guarantees, and he also handled Manziel's endorsement deals coming out of college, which were worth multiple millions over time. Before his rookie season, Manziel signed deals with Nissan, Nike, McDonald's and Panini America, a trading card company.
Manziel and Burkhardt had a mutual connection through Manziel's former offensive coordinator at Texas A&M, Kliff Kingsbury, who is represented by Burkhardt.
Information from ESPN staff writer Jeremy Fowler contributed to this report.