<Page>
UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
FORM 8-K
CURRENT REPORT
Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934
November 6, 2001
Date of earliest event reported
CARRIER 1 INTERNATIONAL S.A.
(Exact name of registrant as specified in its charter)
LUXEMBOURG 001-15693 98-0199626
(State or other (Commission File (IRS Employer
jurisdiction Number) Identification No.)
of incorporation)
ROUTE D'ARLON 3
L-8009 STRASSEN, LUXEMBOURG
(Address of principal executive offices) (Zip code)
(011) (41-1) 297 2600
(Registrant's telephone number, including area code)
In this report "Carrier1 International" refers to Carrier1 International
S.A., a societe anonyme organized under the laws of the Grand-Duchy of
Luxembourg, and "Carrier1," "we," "our" and "us" refers to Carrier1
International and its subsidiaries and their predecessors, except where the
context otherwise requires.
Item 5. OTHER EVENTS
<Page>
On November 6, 2001, Carrier Finance Limited, a limited company
incorporated under the laws of Jersey, Channel Islands and a wholly owned
subsidiary of Carrier1, commenced offers (such offers, the "Offers") to
purchase for cash, upon the terms and subject to the conditions of such
Offers, any and all of Carrier1's outstanding 13.250% Senior Euro Notes due
2009 and 13.250% Senior Dollar Notes due 2009 (together, the "Notes"). As
part of the Offers, Carrier1 Finance Limited is also soliciting consents of
holders of the Notes to certain proposed amendments (the "Proposed
Amendments") to two Indentures, each dated as of February 19, 1999 (the
"Indentures"), between Carrier1 and The Chase Manhattan Bank, pursuant to
which the Notes were issued, which amendments would, among other things,
eliminate or substantially modify certain of the restrictive covenants
contained in the Indentures.
On November 6, 2001, Carrier1 issued a press release indicating that it
intends to launch the Offers, as more fully described in the press release, a
copy of which is filed as Exhibit 99.1 hereto. Further details of the terms
and conditions of the Offers and the Proposed Amendments are more fully
described in the Offers to Purchase and Consent Solicitations Statement
relating to the Offers, a copy of which is filed as Exhibit 99.2 hereto.
Item 7. FINANCIAL STATEMENTS AND EXHIBITS
(a) Financial statements of business acquired. Not applicable.
(b) Pro forma financial information. Not applicable.
(c) Exhibits
99.1 Press Release dated November 6, 2001
99.2 Offers to Purchase and Consent Solicitations Statement dated
November 6, 2001
2
<Page>
SIGNATURE
Pursuant to the requirements of the Securities Exchange Act of 1934,
the Registrant has duly caused this report to be signed on its behalf by the
undersigned hereunto duly authorized.
Dated: November 7, 2001 CARRIER1 INTERNATIONAL S.A.
By: /s/ ROBERT MICHAEL MCTIGHE
--------------------------------
Name: Robert Michael McTighe
Title: Chief Executive Officer and
Director
3