The aim of this paper is to improve knowledge about adhesion strength in single-lap joints by the comparison of data from both nondestructive testing (NDT) and standard mechanical tests. This study presents a high-frequency ultrasonic imaging of aluminum-epoxy-aluminum joints that were carefully chemically prepared using two different surface treatments of the aluminum substrate: silanization and chromic-sulfuric etching. The surface energy of the treated substrate was measured. A complete set of ultrasonic data were obtained using high-frequency focused transducers. After ultrasonic inspection, single-lap shear tests were performed, and the mechanical strength of each joint was determined. The good correlations among the surface measurements, the mechanical tests, and the ultrasonic results are presented and discussed. The demonstration of a close correlation between the ultrasonic images obtained at high frequency and the fracture surface is promising.