The performance of foundation systems on unsaturated soil deposits is considerably influenced by variations of the negative pore-water pressure (i.e., matric suction) distribution within the soil mass due to local microclimate conditions. Although significant understanding has been gained in the last few decades on the behavior of unsaturated soils, the use of unsaturated soil mechanics concepts in the interpretation of field tests has not been incorporated into the state-of-practice. As a consequence, conservative foundation engineering principles are used in practice in regions where unsaturated soil conditions prevail. For example, direct use of field test results (e.g., from plate load tests) obtained during a dry season in unsaturated soil deposits may lead to the selection of unconservatively high design parameters at the site. On the other hand, ignoring altogether the beneficial impact of matric suction on the bearing capacity of soils may lead to unnecessarily expensive foundation systems in tropical, arid climates. This paper investigates the influence of soil suction on the results of plate load tests conducted at a depth of 1.5 m on a structured, naturally occurring lateritic soil. Ten tests were carried out under different soil suction conditions. Matric suction was monitored during plate load testing using tensiometers installed at the bottom of the testing pit up to a depth equal to one plate diameter (0.80 m), which is generally recognized as the influence zone in which significant stress variation occurs (Terzaghi and Peck 1948). The results provide insight into the influence of soil matric suction on ultimate bearing capacity and settlement rate of plate load tests performed on lateritic soils.