Will an iPhone 17 Pro from the USA work in India?

Buying an iPhone in one country to use in another country can have several disadvantages:

Make sure it will work in your country.--> 5G and LTE. Find the iPhone that’s right for your country or region. - iPhone - Supported 5G and LTE networks - Apple or iPad --> iPad - Networks - Apple

You will probably find a lot of overlap but you might not be able to take full advantage of all frequencies.

The iPhone 14, 15 and 16 series devices sold in the US do NOT have a physical SIM slot. Only the current (2024/2025) SE(gen.3) entry level model has them. Check if there's a carrier in your country that offers eSIM service:

Find wireless carriers and worldwide service providers that offer eSIM service on iPhone - Apple Support

Warranty restriction! - Legal - iOS Warranty Document Us - Apple - "IMPORTANT RESTRICTION FOR iPHONE, iPAD AND APPLE TV SERVICE. Apple may restrict warranty service for iPhone, iPad and Apple TV to the country where Apple or its Authorized Distributors originally sold the device."

The warranty does not outright deny warranty coverage in other countries but there are many limitations to the effect Apple almost may well refuse to do repairs under warranty or even repairs at all except in the country of purchase. You may have to negotiate in an Apple Store in person and be willing to reach a compromise with what they have available. If this is not suitable, the device would have to be sent to a friend in the country of purchase to handle any repair claims because Apple will not handle international shipping.

and https://en.wikipedia.org/wiki/List_of_LTE_networks

Since iOS is country specific, not all features might be supported.

iOS and iPadOS - Feature Availability - Apple

The built in hardware might not support all carriers, if it comes to LTE or 5G:

Have a look at this article:

iPhone - Supported 5G and LTE networks - Apple

And the warranty for your Apple Watch may also be restricted to the country of purchase. In case of a warranty claim, you will have to bring it back to the country of purchase. Apple does not ship internationally.

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Apple may restrict warranty service for hardware products to the country where Apple or its Authorized Distributors originally sold the device.

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copied from: Legal - Apple Watch Warranty US - Apple