OPINION OF THE COURT
This appeal concerns a district court order that affirmed its prior order dismissing a complaint without first considering appellant’s request, or her subsequent motion, for leave to amend her complaint. We find that the district court should have granted appellant’s request or her motion for leave to amend, and that the district court thus acted improperly when it dismissеd the complaint without even addressing appellant’s request or motion to amend. Accordingly, we will reverse the order of dismissal and remand to the district court with directions to grant leave to amend the complaint to include an allegation that appelleecorporation’s state of incorporation is Ohio.
I.
This action was brought by the parеnts of Tony W. Kiser, deceased, to recover damages for his allegedly wrongful death.
The initial complaint failed adequately to allege the basis of the district court’s diversity jurisdiction. On February 6, 1986, then-defendant Eaton Corporation (“Eaton”) moved to dismiss the complaint for thаt reason. On February 11, 1986, appellee Parker-Hannifin Corporation (“ParkerHannifin”) joined Eaton’s motion to dismiss. Thereafter, on February 12, 1986, the district court held a telephone conference with counsel for the parties. Counsel for appellant Annie C. Kiser (“Kiser”) was informed at that time that, pending further notification from the court, the pending
One week later, on February 19, 1986, Kiser filed an amended complaint where she again failed specifically to allege the state of incorporation of Parker-Hannifin. The amended complaint did, however, allege that Parker-Hannifin was not a North Carolina corporation.
By letter dated June 24, 1986, Kiser’s counsel asked the district court to vacate its dismissal order, referring to the district court’s February 12th directive deferring consideration of the motions to dismiss. There followed another telephone conference involving counsel and the district court on July 2, 1986, which resulted in an order vacating the dismissal order of June 9, 1986,
3. Plaintiffs and Defendant, ParkerHannifin Corporation shall have thirty (30) days from the date of [the] July 2, 1986 conference within which to attempt to resolve plaintiffs’ claim that diversity jurisdiction is proper; in the event of a failure by plaintiffs and Parker-Hannifin Corporation to reach agreement on this issue, it is Stipulated and Agreed that defendant, Parker-Hannifin Corporation may move the Court upon the end of the said thirty (30) day period for reinstatement of the Order dismissing the Complaint as to Parker-Hannifin Corporation for lack of diversity jurisdiction and/or lack of properly pleading the existence of diversity jurisdiction.
Id. at 1-2.
Kiser’s counsel then attempted to obtain consent to allow her to amend the complaint to allege that Parker-Hannifin’s state of incorporation is Ohio.
On October 8, 1986, Kiser moved for reconsideration of the second dismissal order and, again, for leave to amend her complaint. This motion was accompanied by a proposed second amended complaint stating that Parker-Hannifin is an Ohio corporation. Parker-Hannifin filed its opposition to this motion on October 17, 1986, asserting therein for the first time that the five John Doe defendants destroyed diversity of citizenship.
On December 11, 1986, the district court denied Kiser’s motion for reconsideration and affirmed the second dismissal order, noting that paragraph three of the July 11th stipulation mandated that the parties “shall have thirty (30) days from the date of July 2, 1986 conference within which to attempt to resolve [Kiser]’s claim that di-
versify jurisdiction is proper. The use of the word ‘shall’ indicates that the 30 day time limit was intended to be mandatory, not permissive.” Kiser v. Parker-Hannifin Corp., No. 85-6997, mem. op. at 4 (E.D.Pa. Dec. 11, 1986) [Available on WESTLAW, DCT database] (original emphasis). At the time of this final dismissal order, the district court again did not mention Kiser’s thеn-renewed motion for leave to amend her complaint. Our appellate jurisdiction over this matter is conferred by 28 U.S.C. § 1291 (1982).
II.
The first question we must address is whether the district court erred when it failed to consider Kiser’s motions for leave to amend her complaint prior to addressing Parker-Hannifin’s motions to dismiss. The decision of a district court to grant or deny leave to amеnd is reviewed only for an abuse of discretion. See Zenith Radio Corp. v. Hazeltine Research, Inc.,
In this case, the district court did not mention Kiser’s requests for leave to amend the complaint in either of its memorandum opinions. The only apparent reason for this effective denial of Kiser’s requests was the parties’ failure to resolve the diversity issue pursuant to paragraph three of the July 11th stipulation. See Kiser, No. 85-6997, mem. op. at 4 (E.D.Pa. Dec. 11, 1986) [Available on WESTLAW, DCT database]; Kiser, No. 85-6997, mem. op. at 3-4 (E.D.Pa. Sept. 23, 1986) [Available on WESTLAW, DCT database]. The district court erred, however, when it employed the stipulation to achieve such a drastic result. The stipulation’s only mandate was that the parties “shall ... attempt ” to resolve Kiser’s claim that diversity jurisdiction is proper. Kiser, No. 85-6997, stipulation & order at 1-2 (E.D.Pa. July 11, 1986). It did not direct that the parties, on pain of dismissal, shall resolve Kiser’s claim that such jurisdiction is proper. We note that the record reveals that Kiser did make the requirеd attempt, and we hold that the district court erred when it punished Kiser, by dismissing her complaint, for Parker-Hannifin’s refusal to cooperate with her honest, albeit belated, efforts to allege a basis for the district court’s jurisdiction.
Parker-Hannifin argues that Kiser had been given the time from February 13, 1986, to amend her complaint. This argument fails to take into account the district court’s February 12th statement that no response by Kiser to the dismissal motion was necessary. In addition, Rule 15(a) declares that a party may amend his or her pleading once as a matter of course at any time before a responsive pleading is served. Thereafter, a party may amend his or her pleading only by leave of court or by written consent of the adverse party. See Fed. R.Civ.P. 15(a). Because Kiser had amended her complaint on February 19, 1986, which was prior to the filing of ParkerHannifin’s answer on March 27, 1986, she was thereafter constrained by the mandate of Rule 15(a) from further amending her complaint as a matter of course. Finally, we note that “mere delay is not by itself enough to justify denial of leave to amend.” Sanders,
We are unable to envision any prejudice to Parker-Hannifin from the proposed amendment; because allowing this amendment should not affect Kiser’s tactics or case theories, it will not cause Parker-Hаnnifin undue difficulty in preparing its defense. See Sanders,
III.
The second question before us is whether the district court properly dismissed Kiser’s complaint.. The dismissal of a complaint, by the district court, for failure adequately to allege jurisdiction is subject to plenary review. See Medical Fund-Philadelphia Geriatric Center v. Heckler,
IV.
We must conclude by noting that Kiser has filed with this Court a document from the Sеcretary of the State of Ohio. It certifies that Parker-Hannifin is an Ohio corporation, was incorporated there on December 30, 1938 and has its principal location in Cleveland, Ohio. While this fact of course should have been pled by Kiser in her original complaint, we find it somewhat disturbing that counsel for Parker-Hannifin refuses even to acknowledge that the Ohiо certificate accurately describes ParkerHannifin’s incorporation and place of busi
V.
For the foregoing reasons, we will reverse the dismissal order of the district court and grant Kiser’s motion for leave to amend her complaint.
Notes
. The deсedent’s father, Everett W. Kiser, died on December 18, 1984. Appellant Annie C. Kiser maintains this action as the mother of the decedent and as the duly-appointed administratrix of her husband’s estate.
. A letter to the district court from Leonard A. Busby, Esquire, attorney for Eaton, dated February 13, 1986, stated in relevant part: "Your Honor ... informed counsel [during the telephone conference] that the pending Motions of Eaton Corporation and Parker-Hannifin on the grounds that the Complaint does not properly allege the basis for jurisdiction need not be responded to by plaintiffs pending further notification from Your Honor." Appendix for Plaintiffs-Appellants at 34a. Neither the district court nor counsel has suggested that this letter does not recount acсurately the district court’s directive on this jurisdictional issue.
. Kiser is a citizen of North Carolina.
. Because the record shows that the district court, on February 12, 1986, informed Kiser's counsel that Parker-Hannifin's pending motion to dismiss did not need to be answered pending further notification from the court, and because no such notification was ever given, we conclude that the initial dismissal order of the district court was inadvertent. Apparently recognizing this oversight, the district court properly vacated that dismissal order.
. Kiser’s Motion for Reconsideration of Court's Order Dismissing the Complaint and for Leave to Amend the Complaint alleges that, ”[b]etween July 11, 1986 and August 2, 1986[, her] counsel and counsel for defendant, Parker-Hannifin, agreed that defendant's counsel would attempt to obtain the consent оf his client for [Kiser] to amend her complaint to allege defendant’s place of incorporation.” App. at 133a jf 16. ParkerHannifin’s answer to this motion admits the same. See App. at 151a [[16.
. Although Parker-Hannifin has also raised this issue concerning the effect of the inclusion of the five John Doe defendants in Kiser’s amended complaint on diversity of citizenship in this appeal, to date this issue has not been addressed by the district court. Because Kiser, on remand, may seek leave further to amend her complaint as to these defendants, we decline to issue what may well be an advisory opinion on this issue.
Judge Becker would address this issue, believing that it potentially affects our jurisdiction, and he would dismiss the John Doe defendants on either of two theories. First, noting that John Doe defendants destroy diversity when their citizenship cannot truthfully be alleged, Pullman Co. v. Jenkins,
In sum, because a John Doe pleading is usually problematic and is no boon to anyone, Judge Becker would render John Doe defendants dismissible as a matter of course in federal diversity litigation. See generally 2A J. Moore, J. Lucas & G. Grotheer, Moore’s Federal Practice j[ 8.10 at 8-45 (2d ed. 1987) (absent "unusual circumstances ... the practice [of pleading John Doe defendants] is unwarranted in diversity cases brought originally in the federal courts”).
. We note the following statements from oral argument to this Court:
THE COURT: [A]re you asserting before us that your client doеs not have [its] principal place of business in Ohio____ and [denying that] it’s incorporated in Ohio? MR. O’BRIEN: I frankly don’t know personally, Your Honor____ I can’t assert that one way or another.
THE COURT: You mean [that,] after all of this time[,] with all the counsel fees that have been paid in litigating this[,] that you don’t know [if] — [that you] have not made inquiry as to whether [ — ] your client is incorporated in Ohio and its principal place of business is in Ohio?
MR. O’BRIEN: No. I have not, Your Honor.
