iOS 26.1 causing my iPhone 15 Pro to overheat

Let's define Overheating. Are you seeing a thermometer on your iPhone screen with a message saying your iPhone can't be used until it cools down? If no, your phone is not overheating. Depending on when you installed iOS 26, it can take days of it working behind the scenes to reindex the millions of bytes of data on your iPhone. When a battery works harder, it generates heat.

The first thing I do after any iOS update is Force Restart my phone --> Force restart iPhone - Apple Support

Did you do that after installed iOS 26?

Another thing to check, since you have an iPhone which may be 2 years old at this point is to check your Battery Health. Open Settings > Battery > Battery Health - if your battery is near, at or below 80%, the useful life of the battery has been spent and it's time to pay Apple to replace the battery. Depleted batteries generate more heat doing even simple activities.

The phone / battery is not overheating. My iPhone gets quite hot at times, especially after a recent update, but it never displays the "overheating" message.

I imagine that the techs at the Apple Store / Genius Bar will tell you the same thing if you take the phone in to be checked out. Still it might be a good idea to make an appointment to see if they pick up something unusual.

If you cannot take the phone in, Apple Support can usually run a remote test on your iPhone.

Support

So, you are seeing this message on your iPhone?

Click to open this link: If your iPhone or iPad gets too hot or too cold - Apple Support

stelian130 wrote:

I don’t see that screen. The phone gets very hot on the side where the volume buttons are. This is unusual. As somebody mentioned, I have this phone for 2 years and I never had that overheating before, only after I have installed iOS 26.1.

The battery health is at 89% so still doing good.

i installed the iOS 26.1 after was released and restarted my phone multiple times since then.

A restart is powering the phone off and back on. What I provided above is a Forced Restart, a completely different procedure. Are you saying you actually Force Restarted your iPhone? If no, try it. If things don't improve, schedule an appointment at your Apple Store Genius Bar to have your phone tested.