With 1-(6-methoxynaphthalen-2-yl)ethanone as the starting material, aza-BODIPYs bearing naphthyl groups were successfully prepared. Effect of extended π-conjugation by attaching the naphthyl group on photophysical properties was noticeable. The absorption and emission maxima of aza-BODIPY 4 (λabs=706 nm, λem=733 nm) bearing the naphthyl group were bathochromically shifted compared to these of 1 (λabs=688 nm, λem=715 nm) bearing the phenyl group. Moreover, the main computed photophysical data at the best level of calculation, i.e., cLR-PCM(CHCl3)-M06-2X/6-311+G(2d,p)/SOS-CIS(D), were in agreement with the experimental data. Aza-BODIPY 5 as a photosensitizer (λabs=704 nm in toluene) had moderate singlet-oxygen production having about 2.0-fold rate enhancement when compared to that of methylene blue, and it is thought to be a photosensitizer to be potentially used for the singlet oxygen generation