The Aleutian mink disease (AD) is one of the most serious threats to modern mink breeding. In farms where AD is endemic, a significant effect on breeding and reproductive effects is caused by permanent AMDV infection. The aim of this study was investigating the influence of subclinical infection of AMDV on the functional immune status and on the state of postvaccinal immunity against mink distemper. The analyses involved 30 brown mink females aged 12 weeks and allocated into an experimental group (group I) and control group (group II), with 15 animals in each. The minks from group I originated from the farm with an endemic form of Aleutian disease. The control minks from group II originated from the AMDV-uninfected farm. The dynamics of the growth of specific antibodies was examined after vaccination of the minks from both groups against distemper. Serum levels were determined in both groups with a seroneutralisation assay (SN). Obtaining positive values in the SN test in both groups of animals confirmed the induction of a specific immune response. There were significant differences in the magnitude of the positive SN assay values between the minks from group I and group II at all days of determination. The significantly lower SN values noted in the group minks with subclinical course of AMDV reveal that Aleutian disease can cause a suppressive effect on humoral response after vaccination.