A new organic crystal, N-(4-aminobenzenesulfonyl)acetamide, was identified as a promising candidate for frequency doubling to the blue region. Large square-bipyramidal single crystals up to 8 mm × 8 mm × 18 mm in size have been successfully grown by the slow-cooling technique. Optical transmission of the crystal ranges from 400 to 1100 nm. The dispersions of refractive indices were measured by the minimum-deviation method. The nonlinear-optical d coefficients at 1064 nm were evaluated to be d33 = 6.2 pm/V, d31 = 3.3 pm/ V, and d15 = 2.8 pm/V by the Maker-fringe technique. Type II phase matching was theoretically and experimentally demonstrated when the crystal was pumped at fundamental wavelengths between 762 and 1064 nm. Detailed characteristics of phase-matched second-harmonic generation were evaluated, along with crystal processing techniques such as cutting, polishing, and antireflection coating.