The SBITOP, which tracks the most liquid and highly capitalised stocks on the LJSE, fell 0.64% to 774.56 points after rising 0.43% last Tuesday.
The bourse was closed on December 24, 25 and 26 for Christmas.
Five of the eight blue chips of the LJSE closed lower, two rose and retailer Mercator [LJE:MELR] ended flat at 72 euro ($87.8) on Monday.
Port operator Luka Koper [LJE:LKPG] led the SBITOP decliners, closing down 2.98% at 22.8 euro.
Insurer Zavarovalnica Triglav [LJE:ZVTG] was the biggest blue-chip gainer, adding 3.08% to 23.45 euro.
Drug maker Krka [LJE:KRKG] was the most traded blue chip with 31,356 shares changing hands. The stock shed 0.85% to close at 58 euro.
Total daily turnover on the LJSE rose to 3.0 million euro from 2.1 million euro last Tuesday.
($=0.8211 euro)