Trippier was called up for the England national team for the first time ahead of the upcoming clashes against Scotland and France in June, and the 26-year-old will surely be looking to impress for the Three Lions.
Speaking on Trippier's selection, Southgate said: "I watched him a lot at Burnley, he's got a good mentality, his play in the final third of the pitch is of a high quality, he's one of the best crossers in the league I think and his selection of pass is good.
"It's obviously been an unusual situation, we've had two of our best full-backs both at Tottenham and it's been nice from our point of view that Kieran's had matches towards the end of the season. That's enabled us to have a more realistic case for picking him because he's somebody that we've been following right the way through.
"Kieran impressed me at Burnley in the season they had in the Premier League when he was there and I think he's finished the season very well with Tottenham."