The concept of alternative defendants is related to the rule allowing alternative causes of action and alternative defenses. Suing defendants in the alternative avoids multiplicity of suits. Examples include a pedestrian suing drivers/owners of two vehicles involved in a collision where the cause is uncertain, or an insurance company suing a shipping company and a warehouse company in the alternative for lost goods.

Alternative defendants may be joined when the plaintiff is uncertain against whom of several persons they are entitled to relief. The plaintiff may join any or all of these persons in the alternative. This is permitted even if a right to relief against one may be inconsistent with a right of relief against the other. This rule is found in Rule 3, Section 13 of the Rules of Court.