Turkey's stock exchange fell 0.24 percent, or 243.80 points, to open at 102,166.51 points on Monday.
Among all sector indices, the wholesale and retail trade index posted the best performance, up 0.98 percent, while the leasing factoring index saw the worst, down 0.93 percent.
The BIST banking index and the BIST holding index lost 0.48 percent and 0.23 percent, respectively.
On Friday, Borsa Istanbul's BIST 100 index closed at 102,410.30, up 0.53 percent, with a 4.77 billion-Turkish lira (nearly $1.06 billion) trade volume.
The U.S. dollar/Turkish lira exchange rate increased to 4.5500 as of 9.30 a.m. local time (0630GMT) on Monday. It was 4.4920 at Friday's close.
The euro/lira exchange rate increased to 5.3420, compared with Friday's close of 5.2810.
The price of Brent oil was $78.97 per barrel as of 10 a.m. local time (0700GMT) Monday.