<p>This study investigates the authorship composition of Australian scholarly journals and the factors that influence their national orientation and international reach. Using a dataset of 396 journals (2020–2024), I calculated the Index of National Orientation (INO, for Australian orientation), Author Diversity Index (ADI), and International Collaboration Index (ICI), and examined their relationships with journal characteristics. Findings display that Australian journals are predominantly authored by Australian researchers (45.3%), but international contributions are substantial, particularly from the USA, China, the UK, and New Zealand. The study shows that journal characteristics—such as indexation, publisher type, subject area, open access status and title features—influence their authorship patterns and internationality. Scopus-indexed journals show significantly higher author diversity (ADI) and international collaboration (ICI) compared to non-indexed journals. Physical sciences journals display the highest author diversity, whereas medical and health sciences journals have a stronger national orientation. Publisher type also plays a role, with journals from international commercial publishers having the highest international contribution, while those from government and not-for-profit organisations maintain strong national authorship. Journals with ‘International’ in their title attract the most diverse authorship, whereas those with ‘Australia/n’ or related terms in their title exhibit a strong national orientation. The results confirm the dual role of Australian journals in supporting local research communities while engaging in global scholarship. Policy and sustainability challenges for nationally oriented journals require further attention.</p>