England suffered their second defeat in three days after Delhi successfully chased down their target of 295 with nine deliveries to spare.
After being routed by India A on Sunday, Alastair Cook's side would have thought they had posted an excellent total, reaching 294/5 in their allotted 50 overs, largely thanks to another stand-out knock from Ian Bell, who made 108.
The visitors' bowlers never looked comfortable bowling on a slow surface and Delhi chased down the total with relative ease.
Former Indian international Shikhar Dhawan hit a fine 110, while rookie Milind Kumar - who was playing in only his sixth List A match - ended on an unbeaten 78.
Delhi timed their chase perfectly and Rajat Bhatia - who made 45 not out - kept Kumar comfortable at the crease to see the home side home.
India Under-19 captain Unmukt Chand got things going for Delhi after he took on Steven Finn, who conceded 32 runs in his first five overs. Jade Dernbach shared the new ball with Finn, but he too was unable to curtail Delhi's early onslaught.
Chris Woakes and Samit Patel also couldn't stem the tide, but James Tredwell struck twice in quick succession to peg the hosts back to 122/2 after they were 98/0 when Dhawan reached his half-century.
Chand was the first to go, for 37, chipping Tredwell meakly to mid-on, and Jagrit Anand (four) soon followed suit.
Dhawan carried on in his merry though and was particularly severe on Stuart Meaker, who conceded 55 in his 7.3 overs.
England thought they had their man caught behind with his score on 96, but the umpire disagreed. He followed to put Tredwell into the stands to bring up his century in style. In the end, he fell meekly to Joe Root, lbw for 108, but the damage had already been done.
Dernbach and Finn was brought back into the attack and England thought they had opened the door when bowled Vaibhav Rawal for two, but Kumar was proving a tough nut to crack and passed his half-century off 65 deliveries.
Although England were still in the match with 10 overs to go, Delhi requiring 75 at that point, there were no stopping the batsman and they tucked into Woakes and Meaker in particular to reach the target with nine balls to spare.
Earlier, Ian Bell continued his brilliant limited-overs form as his century propelled England to 294 for five.
The right-hander hit 91 in a total of 175 as England lost their first warm-up game against India A by 53 runs via the Duckworth/Lewis method on Sunday, and he was again at it in the second game.
Bell smashed 108 from 125 balls to lift the visitors to solid total. He shared a 70-run opening stand with captain Alastair Cook (44).
Cook was bowled by Sumit Narwal while Joe Root (10) and Samit Patel (13) were both out cheaply as spinner Varun Sood struck in quick succession to put England slightly on the back foot.
However, Bell kept the innings together and shared a 113-run stand with Eoin Morgan, who gave the his team fresh impetus with 52 from 55 balls.
Bell's innings was eventually ended by Sood, who trapped him lbw, but Morgan found a new partner in Craig Kieswetter with the wicketkeeper hitting three sixes en route to an unbeaten 41 from just 27 balls to boost England to a respectable total.
England opted to rest Jos Buttler, Tim Bresnan and Kevin Pietersen for the match, but seamer Steven Finn was included after regaining full fitness.