Nano-sized metal organic framework-5 (MOF-5) was prepared in the presence of triethylamine (TEA) via consecutive combination of ultrasound (US) and microwave irradiation (MW) methods by exploiting the benefit of obtaining MOF-5 in very short reaction times (∼2 min) and high yields (∼95%). The surface area of MOF-5 was found to be 1203 m2/g. The highly crystalline structure of nano-sized MOF-5 was confirmed by XRD. Vibrational modes and thermal decomposition behavior of nano-sized MOF-5 were verified from ATR FT-IR and TGA results, respectively. Based on SEM and AFM results, MOF-5 nanoparticles are spherical in shape, and their sizes vary in the range of 20–80 nm. The high purity of nanosized MOF-5 was confirmed by XRD and EDS results. A very regular and homogenous distribution of MOF-5 nanoparticles with a size range of 20–30 nm within poly(ethylene oxide) (PEO) electrolyte was clearly observed from SEM results. The reason behind size reduction and homogenous distribution of nano-sized MOF-5 was stated as the elimination of any possible aggregation of MOF-5 nanoparticles due to favorable physical interactions between PEO and surface functional groups of MOF-5 during the solution casting process.