What is a Cause of Action? A cause of action is the act or omission by which a party violates the right of another. What are the essential elements of a cause of action? A cause of action exist of the following essential elements are present: 1. A right in favor of the plaintiff by whatever means and under whatever law it arises; 2. An obligation on the part of the defendant to respect or not to violate such right; and 3. An act or omission on the part of such defendant which violates the right of the plaintiff or constituting a breach of obligation of the defendant to the plaintiff for which the latter may maintain an action for recovery.