Sure it is. It has its prophets like Richard Dawkins and Christopher Hitchens, it uses their writings--among others--as the equivalent of religious texts. That is, their works are proof they are correct in their beliefs.
Atheism operates out of the same fundamental set of rules other religions do. They have a set of beliefs, such as there is no god, nothing more than we can observe as one example, and dogmatically set out to shore up support for it. Atheism worships science. It needn't have every trapping of some other religion to be one. All the fundamental basics are present.
When you take what a Christian, Muslim, or whoever, says about their religion and flip it to an Atheist point-of-view, it still sounds exactly the same. The dogma of Atheism is no different from any other religion. Atheism isn't the "absence of religion" at all. It is the absence of god playing a role in a religion.