At a recent mediation, one defendant proposed a Pierringer agreement (often misspelled “Perringer”) with the plaintiff to cleanly resolve its exposure and exit—leaving the plaintiff to continue solely against the holdout defendant everyone recognized as the problem. Plaintiff’s counsel was new to Pierringers, and I stepped in to map the guardrails, to explain what gets disclosed, what does not, how to amend the pleading to limit the remaining claim to several liability, and how crossclaims fall away.

That moment on a mediation, grounded in my own experience drafting and operationalizing these deals, mirrors where Ontario now is after the Court of Appeal’s recent decision in Cadieux v. Cadieux, 2025 ONCA 40^[1].  The Court has doubled down on the legitimacy and utility of Pierringers, and the bar needs to catch up.

The History of Pierringer

The Pierringer agreement traces its origin to the Wisconsin Supreme Court’s decision in Pierringer v. Hoger, 124 N.W.2d 106 (Wis. 1963)^[2], where the Court approved a settlement device that allowed one defendant to resolve with the plaintiff, exit the litigation, and be shielded from contribution claims, while the plaintiff agreed to pursue only the remaining defendants for their several share of liability.

This innovation solved a longstanding problem under joint and several liability by encouraging partial settlements without unfairly disadvantaging non-settling parties. Ontario courts initially confronted settlement structures, most notably in Pettey v. Avis Car Inc., 1993 CanLII 8669 (ON SC)^[3], where Justice Ferrier (in that case, a Mary Carter agreement, explained below)  emphasized the immediate disclosure obligations such arrangements create.

Since Pettey, Ontario courts, including the Court of Appeal, have steadily reinforced the legitimacy of Pierringer agreements, culminating in their firm endorsement in decisions such as Laudon v. Roberts, 2009 ONCA 383^[4] and most recently in Cadieux v. Cadieux. This trajectory illustrates how a doctrine born in Wisconsin became a cornerstone of Ontario multi-party litigation practice.

What a Pierringer agreement is (in plain English)

A Pierringer is a proportionate-share settlement in multi-party litigation. The plaintiff settles with and dismisses one or more defendants, and the action continues only against the non-settling defendant or defendants. The plaintiff limits the ongoing claim to the non-settling defendant’s several share, and the settling defendant is insulated from contribution and indemnity claims. The amount of the settlement remains privileged.  Only the non-financial terms need to be disclosed. This principle was clearly recognized by the Supreme Court of Canada in Sable Offshore Energy Inc. v. Ameron International Corp., 2013 SCC 37^[5].

Ontario’s Negligence Act provides the statutory backbone for this structure. Courts apportion fault among wrongdoers, plaintiffs can still recover 100 percent from any one joint tortfeasor, and contribution and indemnity is limited to several shares between tortfeasors. The Pierringer model meshes with that framework by removing the settling defendant from the contribution loop and restricting the plaintiff’s remaining claim to the non-settler’s several fault under the Negligence Act.

How Pierringer agreements differ from “Mary Carter” deals

Confusion often arises between Pierringer agreements and so-called Mary Carter agreements, but they are distinct. A Mary Carter agreement leaves the settling defendant in the action, often aligned with the plaintiff, and must be disclosed immediately because it alters the adversarial landscape.

Ontario appellate authority has treated late or hidden disclosure of a Mary Carter as an abuse of process warranting a stay, a principle that the Supreme Court endorsed in Aecon Buildings v. Stephenson Engineering Ltd., 2011 SCC 33^[6][6].  Earlier decisions like Pettey had already established the rule that such agreements must be disclosed at once. In Laudon the Court confirmed that partial settlements require the amount paid to be credited to avoid double recovery.

A Pierringer, by contrast, removes the settling defendant from the litigation entirely and bars contribution rights against them. Disclosure of non-financial terms is still required, but the amount paid remains privileged under Sable.

What the Court of Appeal did in Cadieux

The dispute in Cadieux involved a Pierringer order where the plaintiff resolved with one defendant and continued against another. The non-settling defendant argued that it was prejudiced by the loss of potential recourse against the settling party. The Court of Appeal rejected this argument, finding that when a Pierringer is properly structured within the framework of the Negligence Act, the non-settling defendant is not substantively prejudiced. The non-settler remains liable only for its several share and has no open-ended restitution claim beyond the statutory contribution scheme. The Court therefore upheld approval of the Pierringer.

This holding is significant. It answers a recurring defence objection in multi-party tort files that non-settling defendants are somehow worse off when another defendant settles out. The Court of Appeal made clear that Pierringers do not inherently disadvantage non-settling defendants. They simply reinforce the several-liability principle the statute already envisions.

Where Endean fits

The earlier decision in Endean v. St. Joseph’s General Hospital, 2019 ONCA 181^[7]also illustrates the Court’s approach. There, after a Pierringer with the oral-surgeon defendants, the hospital sought to reduce its exposure by attributing fault to the non-parties. The Court of Appeal held that this could not be used to cut the plaintiff’s recovery. The lesson, consistent with Cadieux, is that once a Pierringer is in place, the focus shifts entirely to the remaining defendant’s own fault and exposure.

The disclosure and privilege balance

Ontario courts have drawn a careful line on what must be disclosed and what remains privileged. Any agreement that changes party alignments or removes a party from the litigation must be disclosed immediately. Delay can attract serious remedies, including a stay of proceedings, as in Aecon. What does not need to be disclosed is the amount of the settlement itself in a standard Pierringer, which is protected by settlement privilege, as confirmed in Sable. This dual rule ensures fairness to the court and the non-settling parties, while preserving the core confidentiality of negotiated amounts.

Why Pierringers will (and should) become more common post-Cadieux

The decision in Cadieux lowers the temperature around prejudice arguments and rewards parties who act pragmatically to narrow the real dispute. Combined with Sable’s protection for settlement amounts and the several-liability logic of the Negligence Act, the Pierringer agreement has become the cleanest mechanism for banking partial peace, simplifying trials, and isolating the truly contested issues of fault.

In practice, that means Ontario litigators should expect to see more of these agreements, particularly in motor vehicle cases, occupiers’ liability matters, municipal liability disputes, construction litigation, and professional negligence claims, where multiple defendants are the norm.