Smart agriculture is a fast-growing research field. From one side, the increase of the human population is always demanding more food production. On the other side, the consciousness of the importance of diet quality requires a more controlled and higher quality production, both in terms of nutrition factors and lower use of pesticides. Thus, it is straightforward to apply the progress in electronics and sensors technology for reaching these different objectives. In this paper, we present an overview of the sensors applied for smart agriculture. Two different categories are presented: sensors for evaluating plant health and fruit conditions and sensors used to monitor the environmental condition where the plants are growing.