The Syrian fell to the ground when he saw his grandfather stepping off the boat in the port of Syracuse in Sicily and kissed the old man's hands.
He told police he had arrived from Sweden, knowing his grandfather was on the boat coming in, ANSA news agency reported.
The arrival was the latest in a wave of landings that have brought more than 3,000 Syrian asylum-seekers to Italian shores so far this year.
"What we are seeing is looking more and more like an exodus. There are entire families fleeing," a Red Cross volunteer was quoted as saying.
The asylum-seekers, who officials said included around 50 children, were packed on a boat measuring around 18 metres (59 feet) in length.
The boat's five Egyptian crew members have been detained pending a police investigation and face possible charges of aiding illegal immigration.
Investigators said the boat had left from Egypt on August 24th and was towed for much of the way by a "mother ship" – a fishing vessel.
It was intercepted by a border patrol in Italian waters after apparently being released from the bigger vessel to complete its journey.
Over 1.9 million Syrians in total have fled their homeland, mostly to neighbouring Arab states and Turkey, since the revolt against President Bashar al-Assad erupted in 2011.
The UN last month said one million children have left the country and two million more have been displaced from their homes inside Syria.