PolyMet: No Material Undisclosed Development Related to Stock Movement

ST. PAUL, Minn.–(BUSINESS WIRE)–PolyMet Mining Corp. ("PolyMet" or the "company") at the request of
Market Surveillance, on behalf of the Toronto Stock Exchange, issued the
following statement:

The company is not aware of any material undisclosed development that
would cause today's upward movement in the company's share price.

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 site, a large processing facility located approximately six
miles from the ore body in the established mining district of the Mesabi
Iron Range in northeastern Minnesota. The NorthMet Final Environmental
Impact Statement was published in November 2015, preparing the way for
decisions on permit applications. 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 January 31,
2017, and in our other filings with Canadian securities authorities and
the U.S. Securities and Exchange Commission, including our Report on
Form 6-K providing information with respect to our operations for the
three and nine months ended October 31, 2017.

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.

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Contacts

PolyMet Mining Corp.
Media
Bruce Richardson, +1
651-389-4111
Corporate Communications
polymetcommunications@polymetmining.com
or
Investor
Relations
Tony Gikas, +1 651-389-4110
Investor Relations
investorrelations@polymetmining.com