Taking first strike after winning the toss, Sri Lanka 'A' hit up a total of 236 for 9 wickets off 50 overs.
England 'A' were done in by the leg-spin of Upul Chandana, who in two successful spells finished with figures of 5 for 46 to dismiss them for 195 in 47 overs.
It was the third successive time in the series that England 'A' were bowled out well inside their quota of 50 overs.
Requiring to score at 4.74 runs per over, England 'A' were unable to keep any big partnerships going until Ashley Giles joined Darren Maddy at the fall of the fifth wicket at 100 in the 25th over.
The two put on 61 off 94 balls before part time off-spinner Mahela Jayawardene separated them by having Giles caught by Chandana at long-on for 26. He also sent back Donggie Brown in the same over for one.
When David Nash was run out by Jayawardene without scoring, England 'A' had lost three wickets for four runs in nine balls.
Maddy and Dean Cosker tried to retrieve the situation by adding 30 for the ninth wicket, but Chandana returning for his second spell sent back Maddy and last man Paul Hutchison within the space of three balls to end the match.
Maddy, the most consistent performer, began the tour with a century and concluded it yesterday with an innings of 70 scored off 94 balls. It comprised of only a solitary four.
Sri Lanka 'A' began their innings with an opening partnership of 51 off 68 balls between Chandika Hathurusingha and Avishka Gunawardana. Hathurusingha went on to make a top score of 51 off 73 balls with four fours and Gunawardana made 25 off 34 balls.
Russell Arnold and skipper Ruwan Kalpage contributed 32 apiece but it was left to Pubudu Dasanayake to see Sri lanka 'A' to a respectable total.
The little wicket-keeper took 12 runs (2 fours and 4 wides) of the final over of the innings bowled by Maddy. He finished unbeaten on 19 with four fours.
left-arm spinner Ashley Giles was the most impressive of the England 'A' bowlers taking 3 for 34 off 10 overs.
With yesterday's game, England 'A' completed their nine-match tour of Sri Lanka winning the unofficial Test series 2-0 (1 drawn) and losing the one-day series 3-0. They left for home yesterday.