Intense competition with lianas (woodclimbers) can limit tree growth, reproduction, andsurvival. However, the negative effects of liana loadson tree allometry have not yet been addressed. Weinvestigated the hypothesis that liana loading on treecrown alters tree’s allometry, expressed throughslenderness (height–diameter ratio). The relationshipbetween trunk slenderness and percentage of treecrown covered by lianas was investigated for 12 treespecies from 10 fragments of the SemideciduousSeasonal Forest in Southeastern Brazil. We also testedwhether the relationship between slenderness andwood density differ between trees without lianas andtrees heavily infested. Liana loads significantly alteredtree allometry by decreasing slenderness, even whenlianas covered less than 25% of tree crown. Heavywoodspecies decreased their trunk slenderness in agreater ratio than light-wood species. Our findingsindicate that liana infestation shifts tree allometry, andthese effects are stronger on heavy-wood tree species.