He is playing his first tournament since suffering serious injuries in a car accident in December 2022 that kept him out of last year's IPL as well as the 50-overs World Cup in India
Morgan smashed a career-best 148, Jonny Bairstow made 90 and Joe Root scored 88 to power England to a commanding 397 for six after opting to bat at Old Trafford.
Dawlat Zadran, who dropped Morgan on 24, and Gulbadin Naib claimed three wickets apiece but spin spearhead Rashid Khan logged the worst bowling figures in the history of the World Cup - 110 runs off nine overs without a single wicket.
Hashmatullah Shahidi (76), Asghar Afghan (44) and Rahmat Shah (46) helped Afghanistan to 247-8, their highest total in World Cup, but it was not enough to avoid their fifth defeat in five matches.
For England, Jofra Archer (3-52) and Adil Rashid (3-66) shared six wickets between them.