Set a target of 169 in 40 overs, the home team was all out for 135 in 38.4 overs.
Pakistan made a terrible start as they lost four wickets for 51 runs before wicket-keeper batsman Arman Khan joined her captain Shamsa Hashmi in a face-saving sixth-wicket partnership of 44 in which Arman contributed a breezy 27-ball 29 which included four fours and one six.
But once leg-spinner Sravanth Naidu sent back Arman, Pakistan’s innings ended without a fight.
During her innings, Shamsa refused many singles because of cramps caused by her long stay at the crease. The Pakistan captain saw two batswomen run out during her 108-minute stay
Shamsa remained top-scorer with a 53-ball 30 that was laced with two fours and a six.
Earlier, the Indian innings was dominated by Diana, who contributed an explosive 58 to help her side reach 168 for five. Diana, who struck seven boundaries in her 66-ball knock, put on 55 for the fifth-wicket with Anagha Deshpande (12).
Pakistan’s bowling was wayward that led to 40 extras being conceded.
Scoreboard
INDIA UNDER-21:
Karuna Jan b Mariam 13
Shweta Rohidas lbw b Nabila 23
Rumeli Dhar lbw b Nabila 12
Diana David not out 58
Savitha Nirala b Urooj 7
Anagha Deshpande c Javed b Sana 12
Priyanka Roy not out 3
EXTRAS (B-4, LB-3, W-31, NB-2) 40
TOTAL (for five wkts, 40 overs) 168
FALL OF WKTS: 1-38, 2-68, 3-75, 4-88, 5-143.
DID NOT BAT: Priti Dimri, Soujanya Manukonda, Sravanthi Naidu, Niranjana Nagarajan.
BOWLING: Shamsa Hashmi 8-2-20-0; Asmavia Iqbal 6-0-31-0; Mariam Butt 6-0-16-1; Uzma Malik 4-0-16-0; Sana Mir 8-0-43-1; Nabila Gulzar 5-0-20-2; Urooj Mumtaz 3-0-15-1.
PAKISTAN:
Sana Javed b Rumeli 6
Taskeen Qadeer run out 14
Nabila Gulzar run out 16
Shamsa Hashmi lbw b Niranjana 30
Shumaila Mushtaq run out 1
Urooj Mumtaz c Savitha b Preeti 2
Arman Khan c Savitha b Naidu 29
Asmavia Iqbal b Niranjana 4
Uzma Malik run out 0
Sana Mir b b Rumeli 6
Mariam Butt not out 2
EXTRAS (B-5, LB-1, W-15, NB-4) 25
TOTAL (all out, 38.4 overs) 135
FALL OF WKTS: 1-14, 2-45, 3-49, 4-51, 5-68, 6-112, 7-123, 8-123, 9-129.
BOWLING: Rumeli Dhar 6.4-1-20-2; Soujanya Nath 8-0-17-0; Priyanka Roy 1-0-10-0; Savitha Nirala 6-1-12-0; Niranjana Nagarajan 8-2-16-2; Priti Dimri 3-0-21-1; Diana David 4-0-21-1; Sravanth Naidu 2-0-17-1.
RESULT: India Under-21 won by 33 runs.
UMPIRES: Siddique Khan and M. Nazir Junior.
MATCH REFEREE: Saadat Ali.