The Nikkei 225 index at the Tokyo Stock Exchange lost 48.17 points to 8,793.05. The Topix index of all first-section issues dropped 0.54 percent or 4.12 points to 757.01.
Major exporters waned on a stronger yen while market participants refrained from aggressive bets ahead of the European summit in Brussels, said Hideyuki Ishiguro, supervisor of investment strategy at Okasan Securities.
Still, the Nikkei index was unlikely to fall too far below 8,800 as selling momentum was not strong, he told Dow Jones Newswires.
The euro bought $1.3181 and 101.03 yen in Tokyo afternoon trade, down from $1.3221 and 101.37 in New York late Friday.
The dollar was at 76.66 yen, flat from New York.
Exporters lost ground as Toyota Motor fell 1.72 percent to 2,789 yen while Sony tumbled 1.83 percent to 1,388 yen.
Canon was down 1.00 percent at 3,435 yen. The firm announced a 0.8 percent gain in full-year net profit after the market closed.
On Friday lower-than-expected US growth figures and a disappointing quarterly report from Chevron kept a lid on US markets.
Official data showed that the US economy grew at an annual 2.8 percent in the fourth quarter, but below average forecasts of 3.2 percent.
The blue-chip Dow Jones Industrial Average closed 0.58 percent lower at 12,660.46, while the tech-heavy Nasdaq rose 0.40 percent to 2,816.55 on a report that Facebook could finally make a move to go public.