Possessive constructions encode a relation between two entities, the possessor and the possessum. For inalienable possession the relation encoded reflects a close, intrinsic connection between the possessor and the possessum (e.g., kinship, part-whole relations) whereas for alienable possession the relation is contingent and extrinsic. The distinction between alienable and inalienable possession, and even between different types of alienable possession, is sometimes overtly marked in the grammar (as in many Oceanic languages) and sometimes only covertly signalled (as in many European languages). In a previous offline study, we found that English attributive possessive phrases containing inherently relational possessums elicited a narrower range of interpretations than those given for phrases containing non-relational possessums (Lichtenberk, Vaid, & Chen, 2011). To the extent that the meaning of inalienable possessive phrases is directly retrievable from the lexical semantics of the relational possessum, we hypothesized that it should be accessed more quickly than the meaning of alienable possessive phrases, which may require additional computation. In the present study we tested this hypothesis using a plausibility judgment task. English adnominal possessive phrases containing relational vs. non-relational possessums each paired with animate or inanimate possessors were presented in the s-genitive form (the N1’s N2). Independently of possessor characteristics, participants were significantly faster at judging plausibility for phrases with relational than those with non-relational possessums. The processing advantage observed for inalienable possession is taken as support for the claim that inalienable possessive relations have a privileged status in the mental lexicon.