<p>Asthma is a leading chronic illness in children worldwide, and school staff are often the first responders when asthma emergencies occur at school. Despite their crucial role, many school staff lack adequate training in asthma management. Online training has emerged as a standardised and scalable solution, but its broader effectiveness remains uncertain. This systematic review aimed to evaluate the effectiveness of online asthma training programmes for school staff. A comprehensive search was conducted across six databases (PubMed, CINAHL, Scopus, Web of Science, ProQuest, and Education Research Complete) in June 2024. Eligible studies included those that evaluated online asthma training programmes targeting school staff (teachers, classroom assistants, and school nurses). The effectiveness of interventions was assessed using the Kirkpatrick evaluation model, which categorises outcomes into four levels: reaction, learning, behaviour, and results. Methodological quality was appraised using the Mixed Methods Appraisal Tool (MMAT). Eight studies met the inclusion criteria with quality scores ranging from 40 to 80%. Interventions identified included web-based modules (<i>n</i> = 4), online classrooms (<i>n</i> = 2), an eBook (<i>n</i> = 1), and a PowerPoint presentation (<i>n</i> = 1). All reported participants’ positive satisfaction with the training and improvements in asthma knowledge (levels 1 and 2). However, none of the studies evaluated behavioural change or organisational outcomes (levels 3 and 4). Most studies had small sample sizes and lacked long-term follow-up, limiting assessment of real-world impact. Online asthma training programmes improve school staff’s knowledge and satisfaction, and appear to be as effective as face-to-face training. However, their impact on behavioural or organisational change remains lacking. Future research should explore long-term effects to support real-world implementation.</p>