Hammond in November suspended the transfer of detainees from British custody after finding evidence of abuse within the Afghan justice system.
The British Defense Ministry said it worked with its Afghan partners to allay concerns about abuse.
"We have been working to identify a safe transfer route to Afghan custody and I am pleased that this work has come to fruition," Hammond said in a statement.
The Defense Ministry said many of the Afghans in British custody were suspected of plotting attacks against British forces on the Afghan battlefield.
Hammond said British forces stationed in Afghanistan would continue detaining and debriefing "enemies on the battlefield" for intelligence purposes before handing them over to Afghan authorities.
The British Defense Ministry gave no indication of the number of Afghans held in British custody.
International forces stationed in Afghanistan are making preparations to end their mission next year. Afghan forces are taking on more responsible for security operations as NATO forces stand down.