Laser ultrasonic techniques are used to investigate interfacial losses in concrete. The experimental methodology uses a pulse ruby laser for optical generation and a heterodyne interferometer for laser detection. Concrete is a heterogeneous material made up of both fine and coarse aggregate. The presence of this aggregate, in addition to voids and flaws, causes elastic wave scattering in concrete. This study examines the propagation of ultrasonic waves in both “plain” mortar and concrete. In addition, it develops a one-dimensional model for the losses due to the interface between the mortar and the aggregate. Laser ultrasonic techniques are essential for this study because they allow for the broad band generation and detection of ultrasonic waves without influencing their frequency content.