The top seed, who last won a title at the Denmark Open Super Series Premier in October 2012, beat Sindhu 21-14, 21-17 in 40 minutes to take home a cheque of $9,000 at the Babu Banarasi Das Indoor Stadium here.
The Olympic bronze medallist had defeated Sindhu during the Indian Badminton League (IBL) also in August 2013.
Last year's runner-up Sindhu once again had to be content with silver in her first ever official Badminton World Federation (BWF) match against Saina.
The Olympic bronze medallist had defeated Sindhu during the IBL 2013
The two Pullela Gopichand proteges entered the stadium to a rousing welcome from a packed house on Republic Day, a national holiday, which also had Uttar Pradesh chief minister Akhilesh Yadav in attendance.
World No.9 Saina got off the blocks quickly, taking a 5-0 lead to the delight of the vociferous crowd. Saina proved too good for Sindhu and extended the gap to 8-1 using her smashes to good effect.
With Saina ahead 11-5, Sindhu's confidence slowly began to grow as she hammered three fantastic down the line smashes to close the scoreline to 12-14. But Saina didn't let her 18-year-old opponent settle down and raced away to a 19-14 lead, winning the game with a irretrievable drop.
The World Championship bronze medallist, however, came back strongly in the second game.
Sindhu returned Saina the favour in the second game and breezed through to a 4-0 lead. She retrieved much better than the first game and took the fight to Saina. But an aggressive World No.9 accepted the challenge and equalised the scoreline at 5-all.
Sindhu still maintained the lead until a backhand smash at the net went straight to her body, giving the Olympic medallist the lead for the first time in the second game (10-9).
The 2009 champion upped the ante and brought down the length of the rallies to increase the gap to 18-12. Sindhu clawed back to 16-20 and also managed to save a matchpoint before missing the final shot to give Saina the crucial win and a break in the 15-month drought.