<p>Aggressive behaviours towards other dogs is a common behavioural issue in pet dogs and frequently occurs during on-lead walks. These behaviour are of significant welfare concern for both dogs and owners, yet research into interventions is limited. Despite this, many professional trainers provide owners with behaviour modification advice. This study explored the perspectives of professional trainers regarding factors contributing to on-lead dog-directed aggressive behaviours and their recommendations for behaviour modification. Ten professional Australian dog trainers were interviewed, and responses were analysed using content analysis. Trainers discussed two broad categories of information. First was their perceptions of on-lead dog-directed aggressive behaviours and their causes. Trainers identified both fear and frustration as underlying emotions. Common contributing factors included restraint by the lead, the influence of owners, socialisation that was inappropriate in several ways, and genetic predisposition. Secondly, trainers described their approach when working with owners to address on-lead dog-directed aggressive behaviours. Elements of environmental management, enrichment, or relationship building were discussed by all trainers. Similarly, all trainers discussed teaching foundational skills away from exposures to other dogs; these always included loose-lead walking, improved dog engagement with the owner, or both. All trainers then recommended controlled exposures to other dogs, although the applications varied. Counterconditioning was the most frequently cited approach, though systematic desensitisation, flooding, and aversive pressure were also mentioned. These findings offer valuable insights into the current practices of Australian dog trainers, although the relative effectiveness of interventions for on-lead dog-directed aggressive behaviours, particularly those implemented by owners, remains unclear.</p>