Two isomeric states of 265Sg, i.e., 265Sga and 265Sgb, proposed in Ch. E. Düllmann and A. Türler were produced in the 248Cm(22Ne,5n)265Sg reaction. Decay properties of 265Sga,b were investigated with a rotating-wheel apparatus for α and spontaneous fission (SF) spectrometry under low background conditions attained by a gas-jet transport system coupled to the RIKEN gas-filled recoil ion separator. Based on genetically correlated α-α(-α) and α-SF decay chains, 18 and 24 events were assigned to 265Sga and 265Sgb, respectively. The half-life T1/2 and α-particle energy Eα of 265Sga were measured to be 8.5-1.6+2.6 s and 8.84 ± 0.05 MeV, respectively, and those of 265Sgb were 14.4-2.5+3.7 s and 8.69 ± 0.05 MeV. As a daughter product of 265Sga ,b, the decay properties of the 3-s isomeric state in 261Rf, i.e., 261Rfb, were also derived: T1/2 = 2.6-0.5+0.7 s, Eα = 8.51 ± 0.06 MeV, and SF branch bSF = 0.82 ± 0.09. These results confirm and refine the decay pattern suggested for the decay chain 269Hs → 265Sga,b → 261Rfa,b → 257No → in Düllmann and Türler. The production cross sections for 265Sga and 265Sgb were determined to be 180-60+80 and 200-50+60 pb at 117.8 MeV, respectively, and they are discussed by comparing with the literature data as well as the theoretical prediction.