Short answer. No. Misjoinder of causes of action is not a ground for dismissal of an action. A misjoined cause of action may instead be severed, on motion of a party or on the court's own initiative, and proceeded with separately, so the case as a whole survives.
What the law says
Misjoinder of causes of action is not a ground for dismissal of an action. A misjoined cause of action may, on motion of a party or on the initiative of the court, be severed and proceeded with separately.
Rule 2, Section 6 — Misjoinder of causes of action. Read the full provision →
The rule directly forecloses dismissal on this ground
The provision could not be more explicit: misjoinder of causes of action is not a ground for dismissal of an action. Combining causes of action that should have been kept separate is treated as a curable procedural defect, not as a fatal flaw that wipes out the whole case, however improperly the claims may have been joined together in the first complaint filed with the court.
Severance, not dismissal, is the actual remedy
Instead of dismissal, the rule provides that a misjoined cause of action may, on motion of a party or on the initiative of the court, be severed and proceeded with separately. The misjoined claim is split off into its own proceeding, while the properly joined claims continue in the original action — the case is reorganized, not thrown out.
Either the court or a party can trigger severance
Severance can happen on motion of a party, meaning a party who spots the misjoinder can raise it and ask the court to act, or on the initiative of the court, meaning the court itself can order severance without waiting for anyone to file that motion. Either route leads to the same outcome: the misjoined claim is separated out into its own case rather than the whole action being lost.
Why this protection matters for a plaintiff who joined claims wrongly
A plaintiff who realizes, or is told by the defendant, that certain claims should not have been combined in one complaint does not need to panic about losing the entire case. The proper response is severance of the misjoined claim into its own action, and understanding that this rule exists should keep a party from abandoning or refiling a case unnecessarily over what is ultimately a fixable joinder problem rather than a fatal defect in the pleading.
A defendant who spots the misjoinder is not entitled to have the whole complaint thrown out on that basis either; the correct move is to move for severance, not for dismissal of the entire case.
Severance leaves each claim to proceed on its own merits
Once a misjoined cause of action is severed, it becomes its own separate case, subject to its own procedural steps going forward, including its own docket number, its own filing requirements, and its own eventual judgment, entirely apart from the claims that remain in the original action. The claims that were properly joined in the first place are unaffected and simply continue in the original case as before, without any need to be refiled.