B4C–Fe–based cermets with various Ni concentrations were produced by tube furnace sintering using the powder metallurgy method. The prepared cermets were sintered at 1000 °C under the argon shroud. Ultrasonic properties such as ultrasonic wave velocities, ultrasonic longitudinal and shear attenuation values, Young's (elastic) modulus, and Poisson’s ratio were determined by the pulse-echo method using 2 MHz and 4 MHz probes. The obtained ultrasonic properties were used to characterize the properties of the samples. It was observed that ultrasonic wave velocities and Young's modulus decreased with increasing Ni concentration. At the same time, ultrasonic attenuation values and Poisson ratio increased with increasing Ni concentration. According to the results, the amount of Ni has an effective role in the structure of the cermets.