In the case of most adults, free ridership of buses, trams and trolley-buses in the city, with a population of just over 400,000, requires that they be registered in the population register as Tallinn residents, Xinhua cited the Estonian Broadcasting Corporation as saying.
All students aged 19 and under, who are listed in the population register, can enjoy free public transport.
City officials have described the step as primarily motivated by environmental and social reasons.
However, some have expressed concern about the 12-million-euro budget shortfall the plan is expected to create.