MAPbBr3 quantum dots in SiO2 mesopores (∼4.4nm) were prepared by the spin-coating method, and their luminescence and nonlinear optical properties were studied by time-resolved photoluminescence (TRPL) and Z-scan techniques. The results showed that the absorption and photoluminescence peaks are at 464nm and 476nm, respectively. The TRPL spectroscopy showed two relaxation processes, a short lifetime (1.04ns) and a long lifetime (4.49ns), attributed to the trap–capture recombination and the electron–hole radiative recombination, respectively. Two-photon absorption (TPA) coefficient was 529cm/GW at 800nm. The nonlinear signal changed from TPA to saturable absorption with increase in light intensity.