The sense of smell is the first sense by which horses determine the suitability of feed for consumption. The aim of the study was to assess the influence of the degree of familiarity with the smell and taste of plants on horses’ olfactory exploration. Behavioural responses of twenty adult horses to nine herbs of three degrees of familiarity—least familiar (unknown in the first trial), known only by smell, and known by smell and taste—were investigated. During the tests, the horses were allowed to explore the individual herbs placed in a crib constructed to prevent them from eating the contents. Horses’ pre-consuming behaviour towards olfactory cues of plants was mainly expressed by different times of exploration. The horses explored herbs known by smell and taste less intensively than those initially unfamiliar, but not less intensively than herbs known only by smell. Thus, having more sensory experience (taste and olfactory) with a plant in the past, horses are often quicker to recognise plants based solely on the sense of smell in the future. The sex and type of the horse (warmblood, pony) may influence responses towards herbs of different levels of familiarity.