European statistics agency Eurostat said the EU gained 1.4 million residents in 2009, increasing the population of the 27-country bloc from 499.7 million to 501.1 million.
63% of the increase - representing nearly 900,000 people - was due to net migration, which accounts for arrivals and departures, while the rest was from births.
The figures reinforce the growing role of immigrants in the EU, which has an ageing population. By 2030 over a quarter of the bloc's inhabitants will be aged over 65, the Washington-based Population Reference Bureau has predicted.
Italy saw the largest total number of immigrants of any EU country, at 318,000. Britain was second with 182,000.
Overall, population increased in 19 EU countries and declined in eight, with the highest rates of growth in Luxembourg, Sweden, Slovenia and Belgium. Lithuania, Latvia and Bulgaria saw the largest overall reductions in population.
Compared with 2008, the rate of net migration dropped significantly from 2.9 per 1,000 people to 1.7 per 1,000.
Natural population growth dropped slightly as well, from 1.2 to 1 per 1,000 people.
Turks and Moroccans topped the list of new EU citizens in 2008, according to Eurostat.
The EU remains a popular destination for migrants and many of them, particularly from Turkey, North Africa and Latin America, are keen to stay long enough to become citizens of countries in the bloc.
(EurActiv with Reuters.)
