Aluminum nitrate cannot be synthesized by the reaction of aluminum with concentrated nitric acid, as the aluminum forms a passivation layer.

Aluminum nitrate may instead be prepared by the reaction of nitric acid with aluminum(III) chloride. Nitrosyl chloride is produced as a by-product; it bubbles out of the solution as a gas. More conveniently, the salt can be made by reacting nitric acid with aluminum hydroxide.