The Islamic Leadership Council of Metropolitan New York represents about 60 congregations and Muslim community organizations in the city.
They said acts of terrorism are forbidden by their religion's teachings.
The group stressed all Muslims should not be blamed for the acts of a few, NY1 website reported.
Its leader also announced a social media campaign to fight recruiting attempts by extremists.
"Our ultimate goal is to raise the level of awareness in a way that helps to inoculate the Muslim community against cries and appeals from elsewhere calling Muslims to violent extremism," said Imam Al-Hajj Talib 'Abdur-Rashid, president of the Islamic Leadership Council.
Group leaders said sermons denouncing terrorism will be given around the city on Friday.
They also said many city mosques will host open houses next month aimed at increasing people's understanding of Islam.