Google Pay will work in all countries where Visa contactless payments are accepted.

We recommend you take your plastic card as a backup as not all merchants allow contactless payments.

You can only perform a limited number of Google Pay purchases without an internet connection.  You will therefore require access to a data network or Wi-Fi connection whilst overseas.  The number of offline purchases available will re-set once you have reconnected your device to an online network (e.g. through a data network or Wi-Fi connection).