FORIMMEDIATERELEASEJanuary8,2018

ColumbiaBankingSystemAnnouncesFourthQuarterandFull-Year2017EarningsReleaseandConferenceCallDate

TACOMA,Washington---ColumbiaBankingSystem,Inc.(“Columbia”NASDAQ:COLB)expectstoreportfourthquarterandfull-year2017financialresultsbeforethemarketopensonThursday,January25,2018.Managementwilldiscusstheseresultsonaconferencecallscheduledforthatafternoonat1:00p.m.PacificTime(4:00p.m.ET).Interestedpartiesmaylistentothisdiscussionbyjoiningoneoftwoways:Option1:Live-streamedeventJointhecallthroughaweb-basedlivestreamed-event.Ifyouchoosethisoption,itisrecommendedthatyoulistenthroughyourphoneorcomputerspeakersandnotdialintotheconferencenumberlistedbelowinoption2.Clickheretoregisterandsavetheeventtoyourcalendar: https://engage.vevent.com/rt/columbiabankingsystemincao~9288084 Pleasetestyourconnectionpriortojoiningtoensureasuccessfuluserexperience.ConnectionTest:ClickHereForsystemrequirements,visitourFAQOption2:Dial-inonlyJointhecallonthedayoftheeventusingthetoll-freenumber:888-286-8956ConferenceID:9288084AreplayofthecallcanbeaccessedbeginningFriday,January26,2018usingthelinkbelow:https://engage.vevent.com/rt/columbiabankingsystemincao~9288084 AboutColumbiaHeadquarteredinTacoma,Washington,ColumbiaBankingSystem,Inc.istheholdingcompanyofColumbiaBank,aWashingtonstate-charteredfull-servicecommercialbankwithlocationsthroughoutWashington,OregonandIdaho.Fortheeleventhconsecutiveyear,thebankwasnamedin2017asoneofPugetSoundBusinessJournal’s“Washington’sBestWorkplaces.”Columbiarankedinthetop30onthe2017Forbeslistofbestbanks.

MoreinformationaboutColumbiacanbefoundonitswebsiteatwww.columbiabank.com.InvestorRelationsContact: InvestorRelations@columbiabank.com253-305-1921

NoteRegardingForwardLookingStatements

Thisnewsreleaseincludesforward-lookingstatementswithinthemeaningofthePrivateSecuritiesLitigationReformActof1995,whichcanbeidentifiedbywordssuchas“may,”“expected,”“anticipate”,“continue,”orothercomparablewords.Inaddition,allstatementsotherthanstatementsofhistoricalfactsthataddressactivitiesthatColumbiaexpectsoranticipateswillormayoccurinthefutureareforward-lookingstatements.ReadersareencouragedtoreadtheSECreportsofColumbia,particularlyitsform10-KfortheFiscalYearendedDecember31,2016,formeaningfulcautionarylanguagediscussingwhyactualresultsmayvarymateriallyfromthoseanticipatedbymanagement.

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