Background: Clear aligners, particularly Invisalign®, are increasingly used for maxillary arch expansion due to their aesthetic appeal and non-invasive nature. However, their effectiveness in achieving predictable results, especially for posterior arch expansion, remains a subject of debate, particularly for adult patients with fully erupted dentition. Aim: This scoping review aims to assess the clinical outcomes, predictability, and effectiveness of Invisalign® for maxillary arch expansion, focusing on key factors influencing treatment success. Methodology: This scoping review followed the PRISMA guidelines and systematically searched multiple electronic databases, including PubMed and Scopus, for studies on arch expansion with Invisalign® and other clear aligners. A total of 8 studies were included, focusing on clinical outcomes, efficacy, predictability, and factors like age, compliance, and treatment protocols. Data extraction and synthesis were performed through narrative analysis, including relevant systematic reviews, randomized controlled trials, and observational studies, ensuring a comprehensive and transparent approach. Results: The studies reviewed reveal that anterior teeth show higher predictability in arch expansion with Invisalign® compared to posterior teeth, where accuracy diminishes. Virtual planning often overestimates achievable expansion, particularly for posterior regions. Factors such as age, compliance, treatment protocols, and attachment use significantly affect outcomes, with attachments improving results, especially for molars. Overall, aligner systems offer moderate-to-high predictability for anterior and premolar regions, but posterior corrections remain challenging, requiring effective planning and adjunctive methods. Conclusion: Invisalign® is a promising option for maxillary arch expansion, particularly for mild to moderate discrepancies in younger patients. However, achieving significant posterior expansion requires adjunctive techniques and careful treatment planning, particularly for adult patients.