Animal emotions are central to the concept of animal welfare. So far, emotions have been investigated in animal welfare science as within-individual phenomena, i.e. coordinating mechanisms that guide the animal to take appropriate action. However, emotions include an important social dimension. The social side of emotions is being intensely investigated in humans, but surprisingly little quantitative data exist for animals. Transfers of emotions among humans, sometimes labelled as different types of empathy, take different forms, varying in their cognitive complexity, in the match between the observed and the induced emotion, and in their time-scale. Sharing of emotions in humans is closely linked to behavioural resonance, i.e. to strong involuntary propensity to automatically synchronize with and imitate behavioural actions of other individuals, and this resonance results in a shift towards positive emotions and closer affiliation. Not all forms of empathy-type interactions may exist in animals, but there is ample evidence that animals often do transfer emotions among themselves, either through inadvertent cues or through specifically evolved signals. One simple and widespread form of emotional transfer among animals is discussed in more detail, namely, the process called emotional contagion that causes animals to shift, upon perceiving animals in an emotional state, their own affective state in the same direction. Because this process can multiply both negative and positive emotions in animal groups, it can be of importance for welfare in domestic and captive animals. Other types of empathy-like phenomena, such as strengthening of affiliative bonds through emotional and behavioural entrainment may also influence welfare of social animals. Paying attention to the social dimension of animal emotions will promote our understanding of animal welfare and may open new ways to affect it positively, but much empirical research into the specific forms of social animal emotionality is needed before these prospects will be turned into practicable knowledge