Physical activity levels decline, and screen-viewing behaviours increase during childhood and adolescence. The transition to secondary school appears to coincide with a sharp decline in physical activity. Parents have the potential to influence their child’s behaviours, yet little is known about their expectations for their child’s physical activity and screen-viewing during this transition. This paper explores parents’ expectations for their children’s physical activity and screen-viewing as they transition from primary to secondary school, and their proposed strategies for managing these behaviours during this time. Forty-two parents of children aged 10–11 years participated in a semi-structured telephone interviews in July 2017 or March 2018. The interview data were analysed via inductive and deductive content analysis to explore parents’ perceptions of physical activity and screen-viewing during the transition, the reasons for their perceptions, and the strategies they intended to implement to help their child balance their behaviours. Most parents expected both physical activity and screen-viewing to increase during this transition. There were several individuals, social and school-level factors influencing these expectations. Overall, parents felt that helping their child balance their activity levels, screen-viewing and homework would be challenging.