Gareth Southgate had named a provisional 33-man squad last week but whittled it down to 26 on Tuesday afternoon.
Johnstone had two spells on loan at Deepdale from Manchester United, his first in 2015 when he was in the North End squad which won promotion from League One via the play-offs - making 25 appearances.
The Preston-born keeper returned for a second stay in January 2016, that a shorter stay of a month in which he played four matches.
Johnstone is now with West Bromwich Albion and is being linked with a summer move away from the Hawthorns
In between his two loan spells, North End had Pickford on loan from Sunderland.
Pickford, who will be England's first choice at the Euros, was excellent in the PNE keeper's jersey.
He played 27 games as Preston found their feet in the Championship, keeping 13 clean sheets.
Sunderland recalled him in January 2016 and 18 months later, sold him to Everton for £25m.
There were no real surprises in the squad Southgate named on Tuesday.
Mason Greenwood withdrew through injury, with Jesse Lingard, Aaron Ramsdale, Ben White, Ben Godfrey, James Ward-Prowse and Ollie Watkins the players who didn't make the final cut.
England are in action on Wednesday night against Austria and then play Romania on Sunday, both friendlies being played at Middlesbrough's Riverside Stadium.
Their first group game in the Euros is against Croatia on June 13, then they face Scotland on June 18 and the Czech Republic four days later.
All three group games are being held at Wembley.
Goalkeepers: Dean Henderson (Man Utd), Sam Johnstone (West Brom), Jordan Pickford (Everton)
Defenders: John Stones (Man City), Luke Shaw (Man Utd), Harry Maguire (Man Utd), Trent Alexander-Arnold (Liverpool), Kyle Walker (Man City), Tyrone Mings (Aston Villa), Reece James (Chelsea), Conor Coady (Wolves), Ben Chilwell (Chelsea), Kieran Trippier (Atletico Madrid)
Midfielders: Mason Mount (Chelsea), Declan Rice (West Ham), Jordan Henderson (Liverpool), Jude Bellingham (Borussia Dortmund), Kalvin Phillips (Leeds)
Forwards: Harry Kane (Tottenham), Marcus Rashford (Man Utd), Raheem Sterling (Man City), Dominic Calvert-Lewin (Everton), Phil Foden (Man City), Jack Grealish (Aston Villa), Jadon Sancho (Borussia Dortmund), Bukayo Saka (Arsenal)
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