Tetragonal $$\text {NaY}(\text {MoO}_{4})_{2}$$ NaY ( MoO 4 ) 2 (NYM) phosphors co-doped with $$\hbox {Yb}^{3+}$$ Yb 3 + and $$\hbox {Tm}^{3+}$$ Tm 3 + ions were synthesized through microwave hydrothermal method followed by calcining treatment. Powder X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and photoluminescence spectra were used to characterize the properties of as-prepared samples. The results show that $$\hbox {Yb}^{3+}$$ Yb 3 + / $$\hbox {Tm}^{3+}$$ Tm 3 + co-doped NYM displayed bright blue emission near 472 and 476 nm ( $$^{1}\hbox {G}_{4}\rightarrow {}^{3}\hbox {H}_{6}$$ 1 G 4 → 3 H 6 transition), strong near-infrared upconversion (UC) emission around 795 nm ( $$^{3}\hbox {H}_{4}\rightarrow {}^{3}\hbox {H}_{6}$$ 3 H 4 → 3 H 6 transition). The optimum doping concentrations of $$\hbox {Yb}^{3+}$$ Yb 3 + and $$\hbox {Tm}^{3+}$$ Tm 3 + for the most intense UC luminescence were obtained, and the related UC mechanism of $$\hbox {Yb}^{3+}$$ Yb 3 + / $$\hbox {Tm}^{3+}$$ Tm 3 + co-doped NYM depending on pump power was studied in detail.