A card-shaped disposable auto-injector includes a two-step safety mechanism to prevent inadvertent use or activation of the injection mechanism. In one aspect, the auto-injector is sized and shaped so as to be easy to carry in a wallet-shaped case. In one aspect, it is rectangular in shape so as to facilitate carrying and storage, and to provide a relatively large amount of surface space for instructional text, diagrams, identifying information, warnings, and the like.