Research question The current study aimed to assess knowledge, attitudes and intentions in relation to fertility preservation among children, by proxy, and adolescents with cancer. Although fertility preservation options have been developed to mitigate the adverse long-term effects of life-saving cancer treatment on fertility, fertility is difficult for children and adolescents to conceptualize, especially when they face a cancer diagnosis. Design This was a descriptive, semi-quantitative analysis. Adolescents and parents of children or adolescents within 6 months of a cancer diagnosis and undergoing gonadotoxic treatment were invited to participate. Seventy-one families completed and returned the study's questionnaire (91 questionnaires) over a period of 26 months. Results The vast majority of participants were aware of the gonadotoxic effects of cancer treatment (85%) and had positive attitudes towards fertility preservation (>90%), but only a portion of them (20%) were willing to take action towards this goal. Although adolescent–parent pairs had similar attitudes towards fertility preservation, adolescents tended to be more sceptical about experimental fertility preservation options. Male post-pubertal cancer patients were more likely to be offered fertility preservation counselling or referral to a specialist in comparison to their younger and female counterparts. Conclusions Fertility preservation care has advanced but there are still gender and age differences in counselling and treatment initiation in the paediatric and adolescent cancer population. Interventions to improve provider–patient–parent communication regarding fertility preservation and to help patients address the observed intention–behaviour gap in relation to fertility preservation options are needed.