Globalisation has brought complexity to construction project management, with challenges like design complexity, evolving stakeholder expectations, and disruptions from the COVID-19 pandemic leading to uncertainties such as cash flow disruptions, schedule delays, and health-related issues. Despite modern management techniques, many project-based organisations face cost overruns, schedule delays, and client dissatisfaction. A literature review emphasises the importance of leadership and communication practices, trust development, collaboration, stakeholder management, and relationship and conflict management in addressing these challenges. This study aims to provide insights into the relationship mechanisms between leadership practices, communication, and project success, introducing a novel framework that encourages practitioners to adopt innovative behavioural practices, helping bridge the gap for empirical evidence-based studies. The methodology involves responses collected randomly from experienced project professionals, employing exploratory factors/multivariate regression to identify five key success factors: effective communication, relationship management, leading by example, self-management, and interpersonal sensitivity, along with 18 contributing behaviour practices that will help address challenges experienced in the Australian construction industry: delays and inefficiencies, supply chain management, communication barriers with multicultural workforce and safety protocols implementation, regulatory and safety compliance, infrastructure demands, skills shortages, sustainability, and new technology adoption. The study identifies high-to-moderate levels of interpersonal and emotional behavioural practices, advocating for people-oriented and relationship-building practices to enhance project success, contributing to improved outcomes by adopting our developed framework. Twofold implications include (1) categorising leadership dimensions into clusters, providing a practical tool for project managers and (2) the key success factors tailored to address sector-specific challenges, enhancing project outcomes.