Annual Shareholder’s Meeting May 24, 2023 Exhibit 99.1

CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS 2 This presentation contains “forward-looking statements” within the meaning of Section 27A of the Securities Act of 1933, as amended, and Rule 175 promulgated thereunder, and Section 21E of the Securities Exchange Act of 1934, as amended, and Rule 3b-6 promulgated thereunder, that involve inherent risks and uncertainties. Any statements about our plans, objectives, expectations, strategies, beliefs, or future performance or events constitute forward-looking statements. Such statements are identified by words or phrases such as “believes,” “expects,” “anticipates,” “plans,” “trends,” “objectives,” “continues” or similar expressions, or future or conditional verbs such as “will,” “would,” “should,” “could,” “might,” “may” or similar expressions. Forward-looking statements involve known and unknown risks, uncertainties, assumptions, estimates and other important factors that could cause actual results to differ materially from any results, performance or events expressed or implied by such forward-looking statements. The following factors, among others, may cause actual results to differ materially from current expectations in the forward-looking statements, including those set forth in this presentation: new, or changes in, governmental regulations or policies; tax legislative initiatives or assessments; more stringent capital requirements, to the extent they may become applicable to us; heightened regulatory requirements resulting from the size of our total assets; changes in accounting standards; any failure to comply with fair lending ad other applicable laws and regulations; lending risks and risks associated with loan sector concentrations; a decline in economic conditions that could reduce demand for our products and services and negatively impact the credit quality of loans; loan credit losses exceeding estimates; the soundness of other financial institutions; changes in oil and gas prices, and declining demand for coal could reduce the demand and credit quality of loans; the availability of financing sources for working capital and other needs; a loss of deposits or a change in product mix that increases the Company’s funding costs; changes in interest rates; changes in inflationary pressures; changes to United States trade policies, including the imposition of tariffs and retaliatory tariffs; competition from new or existing competitors; variable interest rates tied to the London Interbank Offered Rate (LIBOR) that may no longer be available, or may become unreliable, to us; cyber-security risks, including “denial-of-service attacks,” “hacking,” and “identity theft” that could result in the disclosure of confidential information; privacy, information security, and data protection laws, rules, and regulations that affect or limit how we collect and use personal information; the potential impairment of our goodwill; exposure to losses in collateralized loan obligation securities; our reliance on other companies that provide key components of our business infrastructure; events that may tarnish our reputation; the loss of the services of our management team and directors; our ability to attract and retain qualified employees to operate our business; costs associated with repossessed properties, including environmental remediation; the effectiveness of our systems of internal operating controls; our ability to implement new technology-driven products and services or be successful in marketing these products and services to our clients; our ability to execute on our intended expansion plans; difficulties we may face in combining the operations of acquired entities or assets with our own operations or assessing the effectiveness of businesses in which we make strategic investments or with which we enter into strategic contractual relationships; incurrence of significant costs related to mergers and related integration activities; the volatility in the price and trading volume of our common stock; “anti-takeover” provisions and the regulations, which may make it more difficult for a third party to acquire control of us even in circumstances that could be deemed beneficial to stockholders; changes in our dividend policy or our ability to pay dividends; our common stock not being an insured deposit; the potential dilutive effect of future equity issuances; the subordination of our common stock to our existing and future indebtedness; the ongoing impact of the COVID-19 pandemic and the U.S. government’s response to the pandemic; changes in general economic conditions caused by inflation, recession, acts of terrorism, and outbreak of hostilities, or other international or domestic calamities, including wars or international conflicts with respect to which the United States may or may not be directly involved, unemployment, or other economic and geopolitical factors; and the effect of global conditions, earthquakes, tsunamis, floods, fires, and other natural catastrophic events; and the impact of climate change and environmental sustainability matters. The foregoing factors are not necessarily all of the factors that could cause our actual results, performance or achievements to differ materially from those expressed in or implied by any of our forward-looking statements. Other unknown or unpredictable factors also could harm our results. All forward-looking statements attributable to us or persons acting on our behalf are expressly qualified in their entirety by the cautionary statements set forth above and included in our periodic reports filed with the Securities and Exchange Commission, or SEC, under the Securities Exchange Act of 1934, as amended, under the caption “Risk Factors”. Interested parties are urged to read in their entirety such risk factors prior to making any investment decision with respect to the Company. Forward-looking statements speak only as of the date they are made and we do not undertake or assume any obligation to update publicly any of these statements to reflect actual results, new information or future events, changes in assumptions or changes in other factors affecting forward- looking statements, except to the extent required by applicable laws. If we update one or more forward-looking statements, no inference should be drawn that we will make additional updates with respect to those or other forward-looking statements.

FIRST INTERSTATE BANCSYSTEM, INC. OVERVIEW Premier community banking franchise in growing markets throughout the Midwest and Pacific Northwest Corporate Overview Headquarters Billings, MT Exchange/Listing NASDAQ: FIBK Market Capitalization* $3.1 Billion Dividend Yield 5.3% Branch Network 307 banking offices Sub Debt Rating Kroll BBB Financial Highlights Balance Sheet Capital Assets $31.6 Billion Total RB3 12.63% Loans HFI1 $18.2 Billion CET14 10.52% Deposits $24.1 Billion Leverage 7.72% ACL2/LHFI 1.24% TCE5 6.37% 1 Held for investment (HFI) 3 Risk based capital (RBC) 2 Allowance for credit losses (ACL) 4 Common equity tier-1 (CET1) 5 Tangible common equity to tangible assets (TCE) 4 307 banking offices in 14 states * Calculated using closing stock price of $29.86 as of 3/31/2023

BUILDING THE FIRST INTERSTATE FRANCHISE 5

DIVERSIFIED DEPOSIT BASE Total Deposits Non-interest Bearing, 30% Demand, 29% Savings, 33% Time, 8% Deposits by State Montana, 25% Wyoming, 12% Idaho, 7% Washington, 3%Oregon, 11% South Dakota, 15% Nebraska, 9% Iowa, 10% Missouri, 1% Arizona, 3% Colorado, 4% Mix of Consumer and Business Deposits 57% 55% 53% 50% 52% 43% 45% 47% 50% 48% Total Consumer Deposits Total Business Deposits 2018 2019 2020 2021 2022 6 $25.1B As of December 31, 2022

DIVERSIFIED LOAN PORTFOLIO Loans Held for Investment Commercial RE, 47% Construction RE, 11% Residential RE, 12% Agriculture RE, 4% Consumer, 6%Commercial, 16% Agriculture, 4% Loans by Geography Montana, 15% Wyoming, 5% Idaho, 5% Washington, 7% Oregon, 9% South Dakota, 10%North Dakota, 1% Nebraska, 6% Iowa, 10% Kansas, 2% Arizona, 6% Colorado, 8% Other, 16% Total Funded Commitments 40.6% 40.9% 34.3% 33.4% 36.8% Total Funded Commitments 2018 2019 2020 2021 2022 7 $18.1B As of December 31, 2022

CREDIT PERFORMANCE 8 Net Charge-Offs to Average Loans First Interstate Top Peer Quartile Median Peer Average Peer Bottom Peer Quartile 2018 2019 2020 2021 2022 0.00% 0.05% 0.10% 0.15% 0.20% 0.25% Non-Performing Assets to Total Assets First Interstate Top Peer Quartile Median Peer Average Peer Bottom Peer Quartile 2018 2019 2020 2021 2022 0.00% 0.20% 0.40% 0.60% 0.80% 1.00% Allowance for Credit Losses to Total Loan and Leases First Interstate Top Peer Quartile Median Peer Average Peer Bottom Peer Quartile 2018 2019 2020 2021 2022 0.00% 0.25% 0.50% 0.75% 1.00% 1.25% 1.50% 1.75% 1 Source: SNL and company reports 2 The comparison to peers shown throughout this presentation is to our 2022 peers as listed in our 2023 Proxy filing.