Rule 18.Joinder of claims and remedies

Rule 18(a) is broad by design: a party asserting a claim for relief — as an original claim, a counterclaim, a cross-claim, or a third-party claim — may join as many claims as it has against an opposing party, whether those claims are independent of one another or presented as alternatives. Nothing in the rule requires the joined claims to arise from the same transaction or share a common question; the rule lets a party gather every claim it holds against the same opponent into one action.

That reach extends across the different claim types a Delaware civil case can generate. A plaintiff can join unrelated claims in the original complaint, a defendant can join multiple counterclaims, and the same joinder freedom applies to cross-claims between co-parties and to third-party claims once someone is brought into the case.

Rule 18 answers a narrower question than it might first appear to. It governs which claims a party can join once the parties themselves are already in the case together — it doesn't address whether new parties can be added. That's the province of Rules 19 and 20.