The state-run National Bureau of Statistics said the east African country's GDP stood at 69.8 trillion Tanzanian shillings (41.33 billion US dollars) in 2013 after the rebasing, up from a previous estimate of 53 trillion shillings.
The base year for GDP calculations was changed to 2007 from 2001.
"The rebasing of the GDP takes into account new transformations in the economy, such as the ongoing mobile phone revolution in the country," Finance Minister Saada Mkuya told a news conference.
Farming remains Tanzania's economic mainstay, while tourism, mining, communications and financial services are the other key sectors. Tanzania has made big natural gas discoveries, with revenues expected to give a boost to the economy by 2020.
Kenya, East Africa's biggest economy, revised up its GDP by 25 per cent to 53.4 billion US dollars in 2013 after rebasing, from 42.6 billion US dollars previously.