The move was announced by President Thein Sein, who earlier rejected UN calls for an independent inquiry.
The clashes between Rakhine Buddhists and Rohingya Muslims also displaced thousands of people.
The UN welcomed the inquiry, saying it could make "important contributions" to restoring peace.
Secretary-General Ban Ki-moon's spokesman said it could create a "conducive environment for a more inclusive way forward to tackle the underlying causes of the violence, including the condition of the Muslim communities in Rakhine".
A statement on Thein Sein's website said on Friday the 27-member commission would include representatives from different political parties and also religious organisations.
It said the commission would submit its findings next month.
The violence in Rakhine state began in late May when a Buddhist woman was raped and murdered by three Muslims. A mob later killed 10 Muslims in retaliation, though they were unconnected with the earlier incident.
Sectarian clashes spread across the state, with houses of both Buddhists and Muslims being burnt down.
The UNHCR has said that about 80,000 people have been displaced in and around the Sittwe and Maungdaw by the violence.
There is long-standing tension between Rakhine people, who are Buddhist and make up the majority of the state's population, and Muslims.
Most of these Muslims identify themselves as Rohingya, a group that originated in part of Bengal, now called Bangladesh.
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