England recalled the fit-again Durham duo of all-rounder Ben Stokes and fast bowler Mark Wood.
Stokes's season has been blighted by knee and calf injuries and he is expected to play in this match just as a batsman only.
Wood has not appeared for England since a Test against Pakistan in Dubai in October following a longstanding ankle problem.
But he looked sharp while taking four for 25 in Durham's Twenty20 semi-final win over Yorkshire at Edgbaston on Saturday.
England decided against playing Jonny Bairstow as a batsman only, with regular ODI wicket-keeper Jos Buttler behind the stumps.
Pakistan made one change to the side that thrashed Ireland by 255 runs in a one-day international in Malahide last Thursday, with left-arm quick Wahab Riaz replacing Hasan Ali.
That match saw Pakistan's Sharjeel Khan score the third fastest 150 in ODI history.
Pakistan opted against recalling leg-spinner Yasir Shah.
This day/night fixture at south coast county Hampshire's headquarters ground is the first of a five-match series.
Pakistan, now the world's top-ranked Test side after their recent 2-2 series draw in England, are currently a lowly ninth in the equivalent ODI standings.
Teams
England: Alex Hales, Jason Roy, Joe Root, Eoin Morgan (capt), Ben Stokes, Jos Buttler (wkt), Moeen Ali, Chris Woakes, Liam Plunkett, Adil Rashid, Mark Wood
Pakistan: Azhar Ali (capt), Sharjeel Khan, Mohammad Hafeez, Babar Azam, Shoaib Malik, Sarfraz Ahmed (wkt), Mohammad Nawaz, Imad Wasim, Wahab Riaz, Mohammad Amir, Umar Gul
Umpires: Simon Fry (AUS), Rob Bailey (ENG)
TV umpire: Marais Erasmus (RSA)
Match referee: Jeff Crowe (NZL)