Ninety-three per cent of voters backed 50 changes to the constitution, officials said yesterday; turnout was 96%. Critics suggest that such high approval ratings do not reflect voter opinion.
The referendum will change the constitution for the second time in four years. In 1999 Mr Rakhmonov held a plebiscite which extended his term - and that of subsequent presidents - to seven years.
This referendum allows him to stand in the 2006 elections, and serve two more terms. It also removes the 65-year age limit for presidents, enabling him to remain president in 2020, when he will be 67.
Tajikistan is the poorest central Asian state. It borders Afghanistan, and still suffers the after-effects of a long civil war.
It follows other former Soviet states whose long-term rulers have a questionable regard for democracy. Kazakhstan, Kyrgyzstan and Uzbekistan have all extended their leaders' presidency through similar votes.