I went to Chase Bank today for several reasons today, and while there notified them that I would be traveling to Croatia, BiH, and Slovenia. When they input Slovenia into their system, an alert popped up about Slovenia. The bank rep told me there was a chance that my credit and or debit card might be rejected in Slovenia. That would be a problem, obviously. Has anyone had a problem recently with their US credit/debit card transactions not being approved in Slovenia. The bank rep said it would be Chase Bank doing the declining, not the Slovenian merchant. There was no such alert in any of the other countries I am visiting.
I was in Slovenia two years ago and had no difficulty (and I think I primarily used my Chase United MileagePlus credit card), but it sort of sounds as if this might be a recent change on Chase's part. You might try Googling about this to see if you turn up any recent info on other forums.
I was in Slovenia this past memorial day weekend and used my Chase Mileage Plus credit card with zero issues. I have a bank account with Chase but did not use my debit card there so I can't speak to that. Unless something has happened in the last 3 weeks, I think you will be fine, at least with the credit card.
ETA - I also had no problems in Croatia and BiH with that credit card, though fewer places accepted credit cards in Mostar. I did use my Chase debit card for an Uber in Croatia without issue, too.
Never had a problem in Slovenia with a credit or ATM card - have been there a few times, was there just last month again. I used my credit card all over the place.
I have heard of people claiming their bank told them their cards might not work in Slovenia or Croatia, though. I always add travel alerts to my credit and debit cards, and none of my financial institutions has ever warned me about Slovenia, Croatia, or anywhere else, to be honest.
Chase is being very weird lately about where they claim their cards will not work. Several questions have popped up here about it. One of the strangest was that Chase claimed their Debit cards will not work in Denmark but there is no issue with their credit cards there (???).
Hopefully you have another card to take with you from a different issuer just in case what you were told turns out to be true.
I would have a backup option available. Banks often put limits on card usage in certain countries due to increased rates of fraud or theft, and these can change regularly and often. So one person's experience a few months ago might not be relevant to yours.
I have also not had problems in any EU countries, at the least. When Chase told me this spring that my debit card might get declined in central Asia, the plan was that it would trigger an email fraud alert, which I could then respond to on my phone before trying again. (But I did not have occasion to test the plan. Ended up exchanging cash that I had.)
Thanks everyone; I will bring a back up credit card just in case; although it sounds like my Chase card will likely work.