Background <p>The Delphi technique is a structured method for achieving expert consensus and is widely used in health research, including studies involving pharmaceutical sponsors. Although guidance exists for the conduct and reporting of Delphi studies, methodological and reporting practices remain variable. This systematic review aimed to characterise the design, reporting, and transparency of Delphi studies with pharmaceutical sponsor involvement.</p> Methods <p>A systematic literature review identified Delphi studies published between 2020 and 2024 that reported pharmaceutical sponsor involvement. Studies were screened and data extracted using a standardised framework informed by published Delphi guidance. Extracted variables included study aims, panel composition and selection criteria, Delphi process design, consensus definitions, reporting practices, and descriptions of sponsor involvement. Methodological quality was assessed using a four-item framework focused on core Delphi design elements.</p> Results <p>Eighty-two studies met the inclusion criteria. Substantial heterogeneity was observed in study design and reporting. While most studies prespecified a consensus definition, the rationale for consensus thresholds and approaches to handling disagreement were inconsistently reported. Details regarding panel recruitment, feedback between rounds, and statement modification were variably described. Reporting of sponsor involvement also differed across studies. Overall methodological quality varied, with many studies meeting only a subset of core quality criteria.</p> Conclusion <p>Delphi studies involving pharmaceutical sponsors show substantial variation in methodological approaches, alongside incomplete reporting of key design elements and sponsor involvement. More consistent reporting of key design elements and sponsor involvement may improve transparency and interpretability. The proposed TRIAD framework offers a structured approach to support transparent reporting in future Delphi studies.</p>