Jemal Johnson gave Milton Keynes Dons a one-goal advantage in the first leg of the Johnstone's Paint Trophy southern area final tie at Swansea City.
Dons keeper Willie Gueret was in fine form against ex-club Swansea
The home side started brightly at the Liberty Stadium and it took a string of fine saves from Dons goalkeeper Willie Gueret to hold his former club.
Febian Brandy was Swansea's biggest threat but he could not find a finish.
Then in the 69th minute Johnson rifled home a 25-yard winner after Keith Andrews squared a quick free-kick.
Swansea pushed for an equaliser and Tom Butler, Alan Tate and Angel Rangel also had efforts saved by Gueret as MK Dons held on for the win.
Swansea: De Vries, Rangel, Tate, Monk, Painter, Robinson (Butler 56), O'Leary, Way, Anderson (MacDonald 1), Bauza (Duffy 64), Brandy.
Subs Not Used: Austin, Allen.
Milton Keynes Dons: Gueret, O'Hanlon, Diallo, Swailes, Lewington, Cameron (Stirling 64), Navarro, Andrews, Dyer (Baldock 90), Johnson, Gallen (Carbon 89).
Subs Not Used: Howell, Abbey.
Booked: Lewington, Andrews, Navarro.
Goals: Johnson 69.
Ref: Tony Bates (Staffordshire).