92-year-old Gujral died at a private hospital in Gurgaon after a brief illness on Friday.
The Prime Minister and his wife arrived at his residence and paid floral tributes.
In his message, Singh said, "In the sad demise of Gujral, our country has lost a freedom fighter, a great patriot and a great scholar statesman. I join the nation in expressing our grief and sorrow at the demise of great son of India."
Union ministers AK Antony, Anand Sharma and Farooq Abdullah, Punjab chief minister Prakash Singh Badal, BJP's Ananth Kumar and LJP's Ramvilas Paswan were among others who visited the residence.
Gujral will be cremated in Smriti Sthal later in the day.