Silver, palladium, Pd-Ag bimetallic nanoparticles (NPs) were prepared by both conventional and ultrasound methods. The ultrasound method was capable of synthesizing NPs with narrower particle size distribution. The prepared NPs were characterized by different methods such as X-ray diffraction, transmission electron microscopy, high resolution-TEM, UV-vis spectroscopy, scanning tunneling microscopy, and energy dispersive X-ray analysis. The highly stable nanofluids in distilled water (DW) and ethylene glycol without any surfactant were prepared and their electrical conductivity and rheological properties at different volume fractions and temperatures were measured. 26.4 % and 31.58% enhancements in viscosity of ethylene glycol were achieved at 20 oc for the nanofluids of 5% silver and 5% Pd-Ag NPs, respectively. 3975% increase in electrical conductivity of DW at 50 oc was achieved for the nanofluid containing 2% Ag. 7567% and 3841% increases in the electrical conductivity of DW were observed at 25 oc for the nanofluids of 1% Pd a n d 1% Pd-Ag NPs, respectively.