The Harlow Islamic Centre was set alight between 10.30pm and 4am, police said.
Entrances to the building were sealed with foam in a "concerted effort" to start the blaze according to one centre member.
Centre vice-chairman Zia Rehman said: "We have been working very hard within the local community, building bridges and we were hoping we wouldn't have this kind of problem, but in the current climate there are elements within society that are not happy."
Hate attacks against Muslims have risen dramatically since the murder of soldier Lee Rigby by Islamic extremists in May.
Nobody was hurt by the fire and the centre suffered limited damage. Prayers went ahead as normal today.
Police are investigating the incident and Chief Inspector Ed Wells said: "There will be a significant police presence throughout the day to reassure all local residents as we seek to identify those responsible."