Some reports suggest the death toll could be as high as 42, with dozens more injured.
The explosions happened in and around a mosque as Muslims were preparing for afternoon prayers.
No-one has yet said they were behind the bombings, but the Islamist militant group Boko Haram has launched previous attacks in Mubi.
Boko Haram has waged a campaign of violence since 2009 to try to create an Islamic state in northern Nigeria.
The violence has killed about 20,000 people and displaced more than two million.
State police commissioner Abdullahi Yerima said the first blast took place at the mosque at about 13:00 (12:00 GMT) and a second bomber detonated a device nearby as worshippers fled.
Witness Abdullahi Labaran said the first bomber had mingled with worshippers and detonated his explosives shortly before prayers began.
He said people in the mosque then fled towards a market where the second bomber struck.
Mubi has suffered regular attacks by Boko Haram. Last November more than 50 people were killed when suspected militants detonated a suicide bomb inside a mosque in the same town.
And in April, the militants killed more than a dozen people in the nearby northern town of Maiduguri in Borno state.
The group is known to target mosques whose preachers disagree with its views.