Contemporary criminology notes an ever-increasing escalation of aggressive behaviours among Polish society. It is observed a brutalisation of crimes involving both physical and verbal aggression. At the same time, society is paying increasing attention to and condemning aggressive behaviour towards animals. This is manifested in the proposed amendments to the Law on the Protection of Animals. The aim of the article is to show that there is a close relationship between aggression directed against humans and animals perpetrated by the same persons. The article is a report from research conducted by the author. The paper is divided into six parts: introduction presenting the status quaestionis of the problem, research methodology, results of research based on file records, criminological theories explaining aggressive behaviours and conclusions. The basic finding is that there are links between aggression towards people and animals, in particular these links are noticeable with the crime of domestic violence which is penalized under provisions of the article 207 of the Polish Penal Code.