Mr Dewji, whose worth has been estimated at $1.5bn (£1.15bn), was found near a sports facility in Dar es Salaam in the early hours of Saturday morning.
He said in a statement: "I thank Allah that I have returned home safely.
"I thank all my fellow Tanzanians, and everyone around the world for their prayers.
"I thank the authorities of Tanzania, including the police force for working for my safe return."
A car used to dump Mr Dewji has been seized by police, who believe the same vehicle was used at the time of the abduction.
An AK-47 assault rifle, two pistols and several rounds of ammunition have also been taken into custody.
Describing Mr Dewji's rescue, police chief Lazaro Mambosasa said: "We found him there physically fit, and we suspect that the abductors are South Africans because he said they were communicating in one of the vernacular from that country."
Simon Sirro, the inspector general of police, said the kidnappers had demanded a ransom, but did not say what it was or whether it was paid.
Mr Dewji's family had offered a reward of $500,000 (£382,500) for information that would help police find him.
He is the chief executive of the MeTL Group, a Tanzanian conglomerate founded by his father in the 1970s.
SKY News.
