Most of those deaths occurred along a perilous central Mediterranean route used by smugglers operating out of Libya, according to the International Organization for Migration (IOM).
The deadliest month was April, when nearly 1,250 migrants died, some 800 of whom were on board an overcrowded ship that capsized off the Libyan coast, the IOM said. Only 28 people on board survived and were taken to Italy, it said.
Worldwide, an estimated 5,350 migrants died in 2015, according to the Geneva-based IOM. The tally in 2014 was 5,017 deaths, it said.
The estimate of more than 3,770 deaths in 2015 in the Mediterranean compared with 3,270 deaths recorded in 2014, it said.
The record numbers of people dying in an effort to flee conflict and acute poverty are “shocking and inexcusable” said IOM Director General William Lacy Swing in a statement.
“Throughout the year, we have been reminded that much of human mobility is not voluntary” he said. “Tragically we have seen so many who felt they had no option but to leave their beloved homelands and were lost at sea, in the deserts or trapped in the back of lorries they had hoped would carry them to a safer and better life.”
Europe is in the midst of its biggest migration crisis since World War Two, according to the United Nations.
The number of people forcibly displaced worldwide is likely to have surpassed 60 million this year, mainly driven by the war in Syria and other long-term conflicts, the U.N. has said.