The aim of this work is to study the effect of the platinum content (0−1.8 wt % Pt) on the microstructure of an alumina-pillared clay. For this purpose, the nitrogen physisorption data at −196 °C, the micropore size distributions of the supported platinum catalysts, and the hydrogen chemisorption results at 30 °C have been analyzed and compared. The preparation of the catalysts has modified the textural properties of the Al-pillared clay support, giving rise to a loss of surface area and micropore volume. After reduction at 420 °C, the presence of dispersed metallic platinum with mean crystallite size in the 22−55 Å range has been found by hydrogen adsorption. Comparison of all results reveals that the platinum species block the micropore entrances by steric hindrance to nitrogen access as the platinum content increases.