Nonsyndromic orofacial clefting is one of the most frequently occurring congenital conditions. The aim of the study was to investigate the prevalence and nature of reduced olfactory function in patients with nonsyndromic cleft lip and/or cleft palate (NSCL/P) and their unaffected first‐degree relatives. Olfactory function was tested using the Sniffin’ Sticks identification test in patients with NSCL/P, in their unaffected relatives, and in control subjects. MR imaging was performed to measure olfactory bulb (OB) volumes and olfactory sulcus (OS) depths. A reduced olfactory function was seen in significantly more patients with NSCL/P (p = .002) than in control subjects, regardless of the cleft type. Strikingly, unaffected relatives of patients with NSCL/P also had a higher rate of hyposmia (p = .001). In hyposmic patients, the OB volumes (left: p = .01 and right: p = .003) and the depth of the left OS (p = .02) were significantly smaller than in controls. In hyposmic relatives, both OS depths (left: p = .02 and right: p = .03) were significantly smaller. Patients with NSCL/P and their unaffected relatives have an increased prevalence of reduced olfactory function, associated with changes in the central olfactory structures.