Optically active highly concentrated Er3+–Al3+ codoped silica thin films were fabricated on fused silica substrates by sol‐gel method. The synthesis of the Er3+–Al3+ double alkoxide was intended to prevent the optically harmful Er clustering by the selective coordination of Al3+ around Er3+ ions. The molar Er ion concentration was varied from 3811 to 23719 ppm. Photoluminescence (PL) measurements indicated that Er ions were optically active in all films of different Er concentrations. A broadband peak was observed at 1531 nm with the full width at half‐maximum (FWHM) of 42 nm, which corresponds to the 4I13/2→4I15/2 transition. The shape, peak position, and FWHM of the PL signals from the sol‐gel derived Er3+ doped silica were quite comparable to those prepared by other methods. The PL peak showed maximum intensity at an Er concentration of 8535 ppm. This implies the concentration quenching at higher Er concentrations.