Diagnostic overshadowing refers to a phenomenon whereby people with mental health conditions encounter inadequate or delayed medical attention and misdiagnosis. This occurs when physical symptoms are mistakenly attributed to their mental health condition. This paper presents a scoping review focusing on direct causes and background factors of diagnostic overshadowing in the context of hepatitis C infection in people who inject drugs and have concurrent mental health conditions. Despite significant strides in hepatitis C treatment with direct‐acting antiviral drugs, the complex interplay of mental health conditions and physical symptoms necessitates a nuanced approach for accurate diagnosis and effective screening. This review was conducted using Joanna Briggs Institute's methodology for scoping reviews. The databases searched included Medline, Embase, PsycInfo, Global Health, CINAHL and Scopus. This review followed the Preferred Reporting Items for Systematic Reviews and Meta‐Analyses extension for Scoping Reviews (PRISMA‐ScR). The search strategies identified 1995 records. Overall, 166 studies were excluded. Forty‐two (42) studies met the inclusion criteria. Three (n = 3) studies represented direct causes, and 39 (n = 39) with background factors related to diagnostic overshadowing. Studies highlighted six key themes encompassing diagnostic overshadowing, with communication barriers, stigma and knowledge deficiencies being the most prominent. Recognising and addressing diagnostic overshadowing in chronic hepatitis C will lead to increased screening, diagnosis and timely administration of life‐saving antiviral therapy, resulting in profound enhancements in well‐being and health outcomes. Moreover, this proactive approach will play a pivotal role in advancing the global effort towards eliminating hepatitis C by 2030.