Can a Muslim work with a Christian Aid Agency. the purpose of the agency might be spreading christianity.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

We have already issued Fatwa 90962 clarifying that it is permissible for a Muslim to work for non-Islamic organizations that work in the field of humanitarian relief provided some conditions are met, among which is that these organizations should not call people to disbelief; so please refer to the above mentioned Fatwa.

However, since it is generally known that these organizations call to disbelief, then a Muslim should have an insight and not work for them unless the matter about them becomes clear (i.e. they do not invite people to disbelief), and until he asks the scholars and the callers to Allaah who are more aware about such matters.