Last year 150,459 foreigners moved to a permanent Swiss address, down 1.1 percent from in 2104, the state secretariat for migration (SEM) said in a report.
At the same time, the number of foreigners leaving the country in 2015 rose by 6.1 percent from the year earlier to 73,444, the report said.
That left a net intake of 71,495 immigrants for the year, a decrease from 78,902 in 2014, the SEM said.
That marked a drop in net immigration for the second year in a row, although it remained at a relatively high level.
By the end of December 2015, the foreign population of Switzerland stood at close to two million - 1,993,916, according to the official count.
That amounts to almost a quarter of the population.
The pursuit of employment was the major reason for immigration (47 percent), followed by family reunification (31 percent), which included families of Swiss citizens with foreign relatives.
Almost 11 percent came to the country for higher education, training or professional improvement reasons.
Fewer than five percent were classified as asylum seekers (see more below).
Most of the immigrants living in the country came from the European Union.
In 2015, Italians accounted for the biggest group of foreigners in Switzerland (313,725), followed by Germans (301,548), Portuguese (268,067) and French (123,050).
But last year, the French showed the biggest increase in arrivals (6,241), followed by Italians (5,123) and Portuguese (5,057).
Separately, SEM reported that the number of foreigners who filed a request for asylum in 2015 rose to 39,523, significantly higher than the previous year (23,765).
But it noted that close to 1.4 million demands for asylum were made across Europe last year, almost double the rate in 2014, fed by the armed conflict in Syria and Iraq.
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But in Switzerland, the chief demand for refugees came from the North African country of Eritrea (9,966), followed by Afghanistan (7,831), Syria (4,745) and Iraq (2,388).
Of the 28,118 requests for asylum processed in 2015, only a quarter were approved (6,377).