Mount is from Portsmouth, and with the rivalry they hold with the Saints, he is expecting the local crowd to be on his back.
"Yes, I expect some stick. I was born in Portsmouth so I am a Pompey boy and a Pompey fan."
"But I have this badge on at the moment so that doesn't come into play too much. I am looking forward to playing at Southampton and it is a massive game for us," Mount added.
"I trained with Portsmouth, Southampton and Chelsea but being a Pompey boy, I always wanted to play for Pompey.
"When Chelsea came in that was my main goal to go and play for them. Chelsea was a massive team. But I always support Pompey and look at their results."
England host Bulgaria first at Wembley on Saturday, and Mason Mount will be hoping to get his England debut at the national stadium.