Parliamentarians, particularly from her party, greeted Gandhi, who reached the house before the proceedings began. She sat near leader of the house and Finance Minister Pranab Mukherjee in the front row of the treasury benches.
According to Congress sources, Gandhi had been in the US for about two weeks to attend to her ailing mother Paola Maino.
Gandhi, who is also the ruling coalition's chairperson, had left for the US before the monsoon session of parliament, which began July 26.
The Congress had been eagerly awaiting her return as important decisions need to be taken, including on caste-based census, said a party insider.