This 3-wave longitudinal study investigated the developmental trajectories of instrumental helping, sharing and empathic helping across toddlerhood, and how socialisation processes (i.e., parents' and teachers' practices) contribute to these developments. Participants were 50 18-months-olds and 62 24-months-olds, their parents, and daycare teachers, who were followed 6 months and 12 months later. At each wave, toddlers' prosocial behaviours were observed through three laboratory tasks, and socialisation processes were examined through parents' and teachers' self-report at the first and second waves. Instrumental helping increased from 18 to 36 months. Sharing increased from 18 to 30 months. Empathic helping increased from 24 to 36 months. Both parental and teachers' practices predicted prosocial behaviours at the ages when they are still emerging, but the relationship varied by types of behaviour examined. These findings confirm the developmental trajectories proposed in cross-sectional studies and add evidence to the role of socialisation processes in the early development of prosocial behaviour.