Some say Egypt is clamping down as the world looks away
The men were arrested at dawn by authorities and taken from their homes. The group includes several university professors, doctors and other professionals.
All are accused of belonging to an illegal organisation which actively seeks to overthrow the government.
A statement released by the Brotherhood named all 15 of the arrested suspects.
It also criticised the timing of the raid, coming while international focus is directed towards the war in Afghanistan.
"A group of some of the most faithful sons of this people were arrested without committing any offence," it said.
"We deplore this ferocious attack, stressing that it does not serve anybody...we also deplore this attack which breaks the national unity."
Banned organisation
About 60 additional suspected Brotherhood members have been in detention for several months without being charged.
A Cairo court is at present deciding whether to keep 35 of them in custody for an additional 45 days, according to Islamist lawyer Abdel-Moneim Abdel-Maqsoud.
The Muslim Brotherhood has been technically banned since 1954 and calls to legalise the group have been consistently rejected by the government, who claim they are a violent organisation.
Nonetheless, the group, which insists it is committed to legal methods, has succeeded in getting 17 of its candidates elected to parliament as independents. They have formed the largest opposition bloc in the Egyptian assembly.
Human rights
A Brotherhood spokesman said that the arrests may be part of an ongoing crackdown on the organisation, despite its support for the official government's stance on the war against terror.
Human rights activists have also recently voiced concern that the Egyptian authorities may use the war on terrorism to crack down on domestic opponents.