Speaking to reporters here at the party headquarters, she said: "We respect the mandate of the people and I congratulate Modiji and BJP for the victory."
Priyanka Gandhi had arrived at the party headquarters along with her brother and party President Rahul Gandhi to address a press conference.
Her remarks came after Bharatiya Janata Party (BJP) was leading in over 300 of the 542 parliamentary seats.
While Rahul Gandhi lost home turf Amethi to BJP's Smriti Irani, he won from Kerala's Wayanad.
UPA chairperson Sonia Gandhi also won from Rae Bareli.
Priyanka, 47, who was appointed AICC general secretary in-charge Uttar Pradesh (east) in January, did manage to create a buzz during the Lok Sabha polls, but failed to revive the party's hopes for the assembly elections scheduled for 2022.
A distinctive feature of Priyanka's campaign was her aggressive take down of Prime Minister Narendra Modi's policies, and while the jury is still out on why she did not take on the PM from Varanasi, her teasing references to the contest certainly established her as a politician willing to take a challenge head-on.
Another key feature of her foray into politics was her calculative approach allowing her brother and Congress president Rahul Gandhi to take centre-stage, while establishing herself firmly in a supportive role.
Her subtle messaging -- be it speaking in Punjabi, invoking her Delhi roots, or stopping to greet Modi supporters -- helped her establish an immediate connect with the masses. But, it did not translate into votes and despite her several rallies and road shows, most of the Congress candidates ended up third with either the BJP or the SP-BSP-RLD alliance winning in the state.
She, however, had taken a realistic approach from the start when she told party workers that she cannot do magic and they have to first strengthen the party at the grassroots.
Her realism was also evident when she said she had picked candidates in UP who would either win or cut into the BJP's votes. But, analysts feel this may not hold true as the Congress may have taken away votes of the UP gathbandhan.
The BJP is set for another dominant performance in UP and expected to win over 50 seats, according to the trends. The SP-BSP-RLD gave a fight to the BJP on many seats, but seemed to have been blunted by the Modi factor.