Lalu Yadav, 74, was brought to the Delhi hospital from Patna in an air ambulance
Rahul Gandhi visited Lalu Prasad Yadav, the Rashtriya Janata Dal chief, at the All India Institute of Medical Sciences or AIIMS in Delhi on Friday.
Mr Yadav's condition is gradually improving and he is likely to be shifted from the Critical Care Unit to a room in a few days, news agency PTI said quoting a source.
Videos showed the Congress leader exiting the hospital after meeting the RJD chief. He was accompanied by AICC general secretary organisation, KC Venugopal.
Mr Gandhi's party, the Congress, is in alliance with Lalu Yadav's party in Bihar. Lalu Yadav served as the Railway Minister in 2004 in the United Progressive Alliance or UPA government headed by Manmohan Singh.
Mr Yadav, 74, was brought to the Delhi hospital from Patna in an air ambulance two days ago, days after he fractured his right shoulder.
Earlier this week, Tejashwi Yadav, Lalu Yadav's son, had said that his father's condition had shown "improvement" but the decision to take him to Delhi was taken as the doctors at AIIMS are well-versed with his medical history.
The veteran Bihar leader, who is out on bail in a fodder scam case, has been suffering from multiple ailments including renal and cardiac problems besides diabetes. On last Sunday, he had a fall and fractured his shoulder after which the affected area was bandaged.
While in Patna, Bihar Chief Minister Nitish Kumar, ally-turned-rival, visited him at the city hospital and said Mr Yadav's medical expenses will be borne by the state as "that is his right". "We have been old associates. I wish him a quick recovery."
They have been allies and also ran a government with the Congress, though at present Nitish Kumar's Janata Dal (United) is in a pact with the BJP.
On Tuesday, Prime Minister Narendra Modi spoke to Tejashwi Yadav enquired about his father's health.