We demonstrate the output of femtosecond (fs) green and ultraviolet (UV) lasers through second-harmonic generation using type-I phase-matched K3B6O10Br (KBOB) nonlinear optical (NLO) crystals. The wavelengths of the fs green and UV lasers are 515 and 400 nm, respectively. The 1030-nm fs laser is used to pump the KBOB crystal to generate the green output. When the laser pump power reached 880 mW with a repetition rate of 1 kHz, an output power of 235 mW was obtained from the green laser with an optical conversion efficiency of 26.7%. When a pump power of 5.87 W was attained with repetition rate of 10 kHz, a green output power of 1.03 W was generated. The fs UV laser is pumped by an 800-nm fs laser, with 132-mW output power achieved when the pump power was 470 mW with an optical conversion efficiency of 28.1%. The experimental results indicate that the KBOB crystal is a promising NLO crystal for generating fs green and UV lasers because of its excellent NLO properties.