Former Congress President Rahul Gandhi is also going to kickstart his campaign on Sunday. He will be addressing three rallies, two in Mumbai and one in Latur.
Media in-charge of the Congress said that the date and venue of Sonia-Pawar joint rally is being worked out.
Both leaders had held joint rally in April 2014, in Bhandara.
Sonia Gandhi has not been keeping well from many years. She has only made cameo appearances in election campaigns. However, party keeps her name in star compaigners' list.
The party is facing tough battle in the two states after the poll reversal in the general elections. She is likely to address two rallies in Haryana and at least two to three in Maharashtra, said a leader.
Both the Congress and the NCP are facing trust deficit among the cadres and have not been able to arrive at a joint campaign mechanism.
Maharashtra is going to polls on October 21. The party is facing incumbent BJP- Shiv Sena combine.
From the Congress, two former Chief Ministers are in the fray - Ashok Chavan from Bhokar and Prithviraj Chavan from Karad South.