This study addresses honorific agreement in double-subject constructions in Korean from a semantic perspective. The question of which NP triggers honorific agreement with the verb has been highly controversial among scholars. We propose that honorific agreement in double-subject constructions is constrained by semantic distance between NP1 and NP2 in terms of possession and subsidiariness. Using semantic features, we classified NP1-NP2 relations into four types that varied in their degree of possession and subsidiariness, and predicted that honorific agreement with NP1 would be natural in the order of ‘person-attribution’, ‘person-part’, ‘person-possession’, and ‘person-person’ types. To verify our prediction, we conducted an acceptability judgment experiment. Fifty-six adult native speakers of Korean participated in an acceptability judgment task, and were asked to rate the acceptability of different types of double-subject sentences. The verb of each sentence was presented either in the honorific form or in the base form. The analysis of the acceptability judgment data confirmed our predicted order of acceptability. Further, agreement with NP2 was judged as more acceptable when it was a possession or a person. The findings suggest that the acceptability of honorific agreement is affected by semantic constraints, and is gradual across different semantic relation types.