Lithium tetraborate nanoparticles co-doped with various percentages of Cu and Mg impurities were synthesized through the combustion process. Scanning electron microscopy images along with X-Ray diffraction pattern confirmed the shape and structure of the products. The Williamson-Hall equation was used to measure the size of nanoparticles that resulted in approximately 47 nm for the crystallite size. The optical band gap of about 3.7 eV was obtained for the nanostructures from the UV-visible spectrum. Furthermore, the thermoluminescence features the samples under gamma irradiation were studied at ambient conditions. The highest thermoluminescence sensitivity achieved at 0.02 % wt Cu and 0.5 % wt Mg impurities simultaneously. The results show that the co-doped nanoparticles have a linear dose response up to an administrated dose of 30 kGy and about 10% of the thermoluminescence signal fades after 30 days of storage at room temperature.