STORY: Soon after polls closed, an exit poll was published by Sigma Conseil indicating a "yes" vote of 92.3%.
There was no minimum level of participation for the measure to pass and the electoral commission put preliminary turnout at only 27.5%.
The new constitution gives the president power over both the government and judiciary while removing checks on his authority and weakening the parliament.
Opposition parties boycotted the referendum, accusing President Saied of a coup and saying the new constitution he published less than a month ago augurs a slide back towards autocracy.
President Kais Saied ousted the parliament last year and moved to rule by decree, saying the country needed saving from years of paralysis as he rewrote the democratic constitution introduced after Tunisia's 2011 'Arab spring' revolution.