Same-sex marriages recorded in England and Wales will be treated as civil partnerships in the island, Policy and Reform Minister Chris Robertshaw told Tynwald.
In England and Wales, procedures for same-sex couples who are in civil partnerships to convert them to marriage are due to be in place by the end of the year.
The first same-sex marriages took place in March.
Onchan MHK Zac Hall said there would be a lot of concern in the island, particularly among Catholics, if same-sex civil partnerships were automatically transferred to marriage.
Mr Robertshaw confirmed this would not be the case.
Meanwhile, a further 50 relationships from countries around the world will be treated in the Isle of Man as a civil partnership, Tynwald has agreed.
The list includes domestic partnerships in some US states and civil partnerships in Ireland and Jersey.
Mr Hall raised concern the list included relationships which were not as formal as a civil partnership. He asked for the list to be withdrawn so it could be examined further.