Over the last 20 years, the dairy industry has implemented new technologies related to Automatic Milking Systems (AMS). AMS have the potential to maximise milk production and animals’ welfare, thanks to the voluntary milking access, but also to increase the resource efficiency and environmental sustainability of dairy farms. This study assesses the state of the art of research on AMS through a systematic review of patent trends in the last two decades. Patents of the last 20 years were extracted from the EspaceNet database. Terms appearing in title and abstract of a total of 154 patents were processed by text mining approach, ignoring low-frequency and meaningless words, and including stemming analysis to aggregate variant forms of the same word. Four clusters were identified: Components, Sensors, Process and Animal, which weights were 30%, 29%, 25% and 16%, respectively. The patent trend and the top contributing countries were evaluated. Moreover, for each cluster, a words frequency analysis was carried out in order to identify research tendencies. The results showed that the highest number of patents was yielded in the early 2000s, thus indicating the great interest to AMS in the initial period. The main contributing countries were The Netherlands and Sweden. The clusters trend pointed out that the focus on the animal and the sensing technologies was constant over time. In recent years, the priority of research shifted towards process efficiency and components. Detailed analysis of clusters allowed to appreciate an increasing interest in the animal health and body conditions over time (+249% and +391% from 2000 to 2019, respectively). Moreover, the study gave evidence of the evolution of the barn towards more efficient systems. The processes which showed increasing relevance were the ones related to facilities cleaning (+291%) and vacuum-based milking systems. The new sensing technologies focus primarily on imaging, allowing to develop new decision models (+348%). Results suggest that AMS patents are moving their attention towards more efficient and sustainable systems. This trend represents an important opportunity for a significant increase in the sustainability of the dairy sector, not only for animals but also for the farmers through the efficient use of the resources, thus enhancing the perception of sustainability by the consumer.