In subterranean clover, leaf size contributes to plant competitivity; besides, this trait is attributed a diagnostic relevance. The study assessed leaf size variation at two growth stages (60 days after sowing and flowering date) on genotypes belonging to the three main subspecies of the complex, viz. subsp. subterraneum, brachycalycinum, and yanninicum. After 60 days, brachycalycinum showed the largest leaflet area while subterraneum and yanninicum did not differ. Leaf size increase between the two measurements, remarkable in all subspecies, was significantly highest in yanninicum, which showed the largest area at flowering date. The leaflet length/breadth ratio was similar in the three subspecies at both stages. In subterraneum and brachycalycinum this ratio decreased significantly from the first to the second measurement; leaflet area increase seemed depending more on breadth than length increase. Yanninicum showed the longest petiole at flowering, and subspecies ranking for this character paralleled that of leaflet area. Particularly in subterraneum, there was a noticeable genotype variation for all characters. Earlier genotypes tended to have larger leaves after 60 days, and shorter petioles and smaller leaves at flowering date. In subterraneum, the genotype leaflet size decreased on increasing altitude and rainfall, and decreasing temperature of the collection sites. The leaf characters examined fairly confirmed to bear a taxonomic basis. Further assessing the physiological behaviour, particularly the response to defoliation and its agronomic implications, of genotypes characterised by different leaf size is envisageable.