PolyMet Announces Commencement of the Rights Offering and Trading Dates

ST. PAUL, Minn.–(BUSINESS WIRE)–PolyMet Mining Corp. (“PolyMet” or the “company”) (TSX: POM; NYSE
American: PLM) has commenced its previously announced offering of rights
(“Rights”) to purchase common shares of the company to raise
approximately US$265 million in gross proceeds (the “Rights Offering”).

The Rights trade on the Toronto Stock Exchange (“TSX”) under the symbol
“POM.RT” and will cease trading on the TSX at noon (Eastern time) on
June 26, 2019. The Rights also trade on the NYSE American under the
symbol “PLM.RT” and the last day of trading on the NYSE American will be
June 21, 2019.

Pursuant to the Rights Offering, all eligible registered shareholders of
PolyMet (subject to applicable law) have been distributed one Right for
every common share of PolyMet owned on the record date of June 3, 2019.
For each one (1) Right held, holders are entitled to acquire 2.119069
common shares of PolyMet at US$0.3881 per share (the “Rights Price”).
The Rights Offering includes an additional subscription privilege
entitling holders of Rights who have fully exercised their Rights to
subscribe for additional common shares, if available, that were not
otherwise subscribed for under the Rights Offering.

Subject to applicable law, all PolyMet shareholders have the choice to
participate and, by exercising all of their Rights, maintain their
existing levels of ownership. Rights holders can, in whole or in part,
exercise their Rights and subscribe for common shares, or sell or assign
their Rights to another party (who wishes to subscribe for new PolyMet
common shares). The expiry time (the “Expiry Time”) of the Rights
Offering is 5:00 pm (Eastern time) on June 26, 2019 (the “Expiry Date”).
Rights not exercised before the Expiry Time on the Expiry Date will be
void and of no value.

As previously disclosed, PolyMet has entered into a standby purchase
agreement (the “Standby Purchase Agreement”) pursuant to which Glencore
AG (“Glencore”), subject to certain terms and conditions and
limitations, has agreed to exercise its basic subscription privilege in
full and to purchase at the Rights Price, that number of common shares
equal to the difference, if any, of (x) the total number of common
shares offered pursuant to the Rights Offering minus (y) the number of
common shares subscribed for pursuant to the basic subscription
privilege and the additional subscription privilege. As a result,
subject to the satisfaction of the terms and conditions of the Standby
Purchase Agreement, the Rights Offering will be fully backstopped by
Glencore.

Shareholders in North America should direct questions to Shorecrest
Group at:

North American Toll-Free 1-888-637-5789
Banks and Brokers and
collect calls 647-931-7454
Email at [email protected]
| www.shorecrestgroup.com

Shareholders outside of North America should direct questions to
Georgeson at:

Shareholders, Banks and Brokers +44 207 019 7081
[email protected]

Further details concerning the Rights Offering are contained in the
company’s short form final prospectus dated May 24, 2019, which is
available on the company’s SEDAR profile and in the company’s Form F-10,
as amended, filed with the U.S. Securities and Exchange Commission on
EDGAR (available at www.sec.gov).

This news release does not constitute an offer to sell, nor the
solicitation of an offer to buy, the securities in any jurisdiction; nor
shall there be any sale of securities mentioned in this news release in
any jurisdiction in which such offer, solicitation or sale would be
unlawful prior to registration or qualification under the securities
laws of such jurisdiction.

About PolyMet
PolyMet Mining Corp. (www.polymetmining.com)
is a publicly traded mine development company that owns 100 percent of
Poly Met Mining, Inc., a Minnesota corporation that controls 100 percent
of the NorthMet copper-nickel-precious metals ore body through a
long-term lease, and owns 100 percent of the former LTV Steel Mining
Company processing facility, located approximately seven rail miles from
the ore body in the established mining district of the Mesabi Iron Range
in northeastern Minnesota. Poly Met Mining, Inc. has completed its
Definitive Feasibility Study and received all permits necessary to
construct and operate the NorthMet Project. NorthMet is expected to
require approximately two million hours of construction labor, create
approximately 360 long-term jobs directly, and generate a level of
activity that will have a significant multiplier effect in the local
economy.

PolyMet Disclosures
This news release contains certain
forward-looking statements concerning anticipated developments in
PolyMet’s operations in the future. Forward-looking statements are
frequently, but not always, identified by words such as “expects,”
“anticipates,” “believes,” “intends,” “estimates,” “potential,”
“possible,” “projects,” “plans,” and similar expressions, or statements
that events, conditions or results “will,” “may,” “could,” or “should”
occur or be achieved or their negatives or other comparable words. These
forward-looking statements may include statements regarding the ability
to receive environmental and operating permits, job creation, and the
effect on the local economy, or other statements that are not a
statement of fact. Forward-looking statements address future events and
conditions and therefore involve inherent known and unknown risks and
uncertainties. Actual results may differ materially from those in the
forward-looking statements due to risks facing PolyMet or due to actual
facts differing from the assumptions underlying its predictions.

PolyMet’s forward-looking statements are based on the beliefs,
expectations and opinions of management on the date the statements are
made, and PolyMet does not assume any obligation to update
forward-looking statements if circumstances or management’s beliefs,
expectations and opinions should change.

Specific reference is made to risk factors and other considerations
underlying forward-looking statements discussed in PolyMet’s most
recent Annual Report on Form 40-F for the fiscal year ended December 31,
2018, and in our other filings with Canadian securities authorities and
the U.S. Securities and Exchange Commission.

The Annual Report on Form 40-F also contains the company’s mineral
resource and other data as required under National Instrument 43-101.

The TSX has not reviewed and does not accept responsibility for the
adequacy or accuracy of this release.

Click
here to subscribe to Mobile Alerts for PolyMet Mining Corp.

Contacts

Media
Bruce Richardson, Corporate Communications
Tel:
+1 (651) 389-4111
[email protected]

Investor Relations
Tony Gikas, Investor Relations
Tel:
+1 (651) 389-4110
[email protected]