The party, which is a constituent of the NDA governments at the Centre and in Maharashtra, also criticised Prime Minister Narendra Modi for describing Priyanka's entry into politics as dynastic politics.
Terming Priyanka as a "trump card" for the Congress, it said, "If people have accepted the legacy of this (Gandhi) family, then why do others have a problem with it?"
Priyanka, whose entry into politics was a guessing game for several years, formally made her foray, with the Congress appointing her General Secretary in-charge of crucial Uttar Pradesh state's eastern part.
"The Congress has appointed Priyanka Gandhi Vadra at the right time. She is a trump card for Congress," Shiv Sena leader Sanjay Raut told ANI.
Showering praise on Rahul Gandhi, he said the Congress president doesn't give false assurances. "Till now, he has not (given false assurances) as he is not in power," he elaborated.
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Entry of Priyanka into politics is "a very good bet" by Rahul Gandhi, an editorial in Shiv Sena's mouthpiece 'Saamna' said, adding the Congress will definitely benefit in Hindi-speaking areas.
"With this step, Rahul Gandhi has shown that he is ready to do everything to achieve success in the forthcoming Lok Sabha elections," it added.
"Some people are spreading the rumour that Rahul Gandhi failed (and) that's why Priyanka was brought. But there is no substance in this theory," the editorial said.
It also showered praise on the Congress president, saying he was cornering the government and leading his party to victory in Assembly elections in three states last month.
"Congress president Rahul Gandhi cornered the government on Rafale (fighter deal). Even if we ignore that, the fact remains that Congress has snatched three important states from BJP. Not giving credit to him for the same is only a sign of frustrated tendencies," the editorial said.
The Sena mouthpiece also referred to the cases against Priyanka's husband Robert Vadra, saying there was speculation that his wife could be pressurised through these.
However, she has put all that aside to officially take a plunge into active politics, it added.
The editorial said the BJP leadership has bitterness for Nehru-Gandhi family "because this family can challenge the BJP, and it is feared that in 2019 it can create problems in getting the majority figure".
It compared Priyanka with former Prime Minister Indira Gandhi, saying the 47-year-old looks like her late grandmother and has a similar talking style.
"Rahul Gandhi has made a very good bet. If this yields results and crowd starts gathering in Priyanka's public rallies, then she can very well prove to be a key leader similar to Indira Gandhi," the Sena mouthpiece said.