Appellants Christopher Owens and Cynthia Hutchins appeal from the district court’s order dismissing their Title VII action against Kaiser Foundation Health Plan, Inc. (“Kaiser”) based on the doctrine of res judicata. We affirm because we conclude that the application of the doctrine of res judicata is not barred merely because they did not receive “right to sue” letters from the Equal Employment Opportunity Commission (“EEOC”) until after their earlier action had been dismissed with prejudice.
I
Appellants are African-Americans who were employed as regional chartroom *711 clerks in Kaiser’s facility in Downey, California. Kaiser relocated the facility from Downey to Ontario, California in February, 1994, at which time Appellants’ employment was terminated. Thereafter, Appellants filed discrimination charges with both the EEOC and the California Department of Fair Employment and Housing, alleging that Kaiser failed to relocate them to another facility because of their race.
On February 14, 1995, Appellants filed an action in California state court against Kaiser, two individual supervisors, and Appellants’ union, asserting causes of action for breach of implied-in-fact contract, breach of the implied covenant of good faith and fair dealing, intentional infliction of emotional distress, and fraud. The Defendants removed the action to federal court. Kaiser moved to dismiss the action based on federal preemption and the applicable statute of limitations. Appellants stipulated to a dismissal. The court dismissed without prejudice on June 19,1995. On November 8, 1995, Appellants amended their charges of discrimination with the EEOC, adding allegations of hostile work environment and racial discrimination.
On November 22, 1995, Appellants filed a second action in state court against the same Defendants. They alleged the same causes of action, with the addition of a claim for breach of the duty of fair representation. The complaint alleged that Kaiser filled positions “with less qualified non-Blacks” and that this action was not based on seniority, “but was instead arbitrary and discriminatory against several African American employees.... ” Defendants again removed the action to federal court and Kaiser moved to dismiss. Appellants did not file a response to Kaiser’s motion. The district court, noting that no opposition had been filed and that Appellants’ attorney had failed to respond to the court’s repeated inquiries, dismissed the action with prejudice on October 25, 1996.
On April 4 and May 9, 1997, respectively, Owens and Hutchins received their “right to sue” letters from the EEOC. Shortly thereafter, they filed a pro se action in federal court solely against Kaiser, alleging that their terminations were unlawfully based on race. Kaiser moved to dismiss the action for failure to state a claim. The district court granted Kaiser’s motion, and dismissed the complaint with leave to amend.
Appellants, now represented by counsel, filed an amended complaint on May 12, 1998 alleging that Kaiser had violated Title VII. Specifically, they alleged that Kaiser permitted a “racially discriminatory and hostile work environment” and that their terminations were “the result of racial, color, and cultural discrimination.” The district court denied Kaiser’s motion to dismiss the amended complaint for failure to state a claim. Kaiser filed its answer on August 31, 1998, and discovery commenced. The court stayed all proceedings from November 9, 1998 to January 13, 1999, however, in order to investigate whether Appellants’ attorney was licensed to practice law.
On May 10, 1999, after discovery had resumed, Appellants moved to file a second amended complaint seeking to add claims for harassment and discrimination under state law. On May 20, 1999, before the district court had ruled on Appellants’ motion, Kaiser moved to file an amended answer to assert res judicata as an affirmative defense and for judgment on the pleadings based on that doctrine. Kaiser argued that the court’s dismissal with prejudice of Appellants’ previous action barred any further action by Appellants based on the same underlying facts. The district court granted Kaiser’s motion to amend its answer, denied Appellants’ motion to amend their complaint as moot, and dismissed the action based on res judicata. Appellants filed a timely notice of appeal. We have jurisdiction pursuant to 28 U.S.C. § 1291.
II
Appellants contend that the district court abused its discretion by permitting
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Kaiser to amend its answer to assert res judicata as an affirmative defense. They contend that Kaiser’s motion was untimely, submitted in bad faith, and prejudicial. We review the district court’s decision to permit Kaiser to amend its answer for an abuse of discretion.
Islamic Republic of Iran v. Boeing Co.,
A district court “shall grant leave to amend freely hvhen justice so requires.’ ”
Lopez v. Smith,
Appellants contend that Kaiser acted in bad faith because Kaiser failed “to offer a plausible explanation for their delayed res judicata application.” We disagree. Kaiser offered substantial competent evidence to explain the delay. Kaiser substituted counsel shortly after Appellants filed their first amended complaint, and offered evidence that new counsel had not represented Kaiser in the prior action and was not aware that the prior action had been dismissed with prejudice. Moreover, Kaiser’s new counsel offered a credible explanation for his belated discovery that Appellants’ action was barred by res judicata: He researched the procedural history of the action in the course of determining whether to oppose Appellants’ motion to file a second amended complaint. Immediately upon learning of the availability of the res judicata defense, Kaiser moved to amend its answer. The district court did not clearly err in finding that Kaiser did not act in bad faith.
Appellants also contend that they suffered prejudice when Kaiser was permitted to amend its answer. This assertion also lacks merit. The amendment caused no delay in the proceedings and required no additional discovery.
See Lockheed Martin Corp. v. Network Solutions, Inc.,
Appellants further argue that the district court abused its discretion because Kaiser unreasonably delayed the filing of its motion to amend. As discussed
supra,
Kaiser moved to amend as soon as it became aware of the applicability of the res judicata defense. Assuming
arguendo
that Kaiser had unreasonably delayed the filing of the motion to amend its answer, “[ujndue delay by itself ... is insufficient
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to justify denying a motion to amend.”
Bowles v. Reade,
Ill
Appellants alternatively contend that Kaiser waived its right to assert the doctrine of res judicata by failing to raise it as an affirmative defense in its answer or in its prior motions to dismiss. We review this issue de novo.
Kern Oil & Refining Co. v. Tenneco Oil Co.,
As discussed
supra,
Appellants were not prejudiced by Kaiser’s late assertion of res judicata. Indeed, Appellants may not demonstrate prejudice based solely on the untimely assertion of res judicata because this affirmative defense would have been dispositive had Kaiser asserted it when the action was filed.
See Wyshak v. City Nat’l Bank,
IV
Appellants also contend that the district court erred in granting Kaiser’s motion for judgment on the pleadings. We review de novo an award of judgment on the pleadings.
Nelson v. City of Irvine,
“Res judicata, also known as claim preclusion, bars litigation in a subsequent action of any claims that were raised or could have been raised in the prior action.”
Western Radio Servs. Co. v. Glickman,
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“The central criterion in determining whether there is an identity of claims between the first and second adjudications is ‘whether the two suits arise out of the same transactional nucleus of facts.’ ”
Frank v. United Airlines, Inc.,
Appellants also challenge the district court’s conclusion that the dismissal of their prior action was “an adjudication on the merits.” This argument fails because the prior action was dismissed with prejudice “based upon plaintiffs’ failure to prosecute.” Unless otherwise specified, such a dismissal “operates as an adjudication upon the merits.” Fed.R.Civ.P. 41(b). Thus, “involuntary dismissal generally acts as a judgment on the merits for the purposes of res judicata....”
United States v. Schimmels (In re
Schimmels),
Appellants further contend that res judicata should not bar review on the merits because their counsel failed to oppose Kaiser’s motion to dismiss in the previous action. The Supreme Court has made clear, however, that there is “no principle of law or equity which sanctions the rejection by a federal court of the salutary principle of
res judicata.” Federated Dep’t Stores, Inc. v. Moitie,
V
Finally, Appellants argue that res judicata cannot apply because they were barred from bringing their Title VII claims in the previous action in light of the fact that they had not yet received their “right to sue” letters from the EEOC.
1
Though we have never addressed this issue in a published opinion, we now join our sister circuits in holding that Title VII claims are not exempt from the doctrine of
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res judicata where plaintiffs have neither sought a stay from the district court for the purpose of pursuing Title VII administrative remedies nor attempted to amend their complaint to include their Title VII claims.
See Heyliger v. State Univ. & Cmty. College Sys. of Tenn.,
Appellants had ample time to secure “right to sue” letters prior to filing their first action in November of 1995. Alternatively, they could have sought a stay from the district court pending their administrative proceedings before the EEOC. In light of Appellants’ failure to exercise either option, we conclude that their Title VII claims are barred by the doctrine of res judicata.
AFFIRMED.
Each party shall bear its own costs.
Notes
. Title VII requires that a plaintiff obtain a “right to sue” letter from the EEOC before filing an action.
See Valenzuela v. Kraft, Inc.,
