Cognitive behavioural therapy (CBT) has heightened the need for internet-delivered intervention for depression with chronic diseases than a traditionally-based treatment procedure, and the need for CBT as an internet-delivered intervention has increased because it scales down the stigma of proceeding to a therapist, saves travel time from different geographical areas, and increases access to the service. This study aimed to evaluate the contemporary evidence for the effectiveness of internet-delivered cognitive behavioural therapy (CBT) as a treatment option for depression with chronic illness (CVD, diabetes, chronic pain, cancer, and chronic obstructive pulmonary disease (COPD)) among adult populations in high-income countries. A systematic search strategy was devised based on selecting search terms, inclusion and exclusion criteria, and refinement processes. Electronic searches were conducted using databases related to healthcare and containing peer-reviewed literature: the Cumulated Index to Nursing and Allied Health Literature (CINAHL), the Excerpta Medica Database (Embase), the Medical Literature Analysis and Retrieval System Online (Medline), and PsycINFO. Key search terms were applied to all databases and combined using Boolean operators to maximise the efficiency of the search. This review included randomised controlled trials (RCTs) evaluating the adult population aged ≥18 years published from 2006-2021. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement was employed to guide the review process. The initial search yielded 134 studies across all databases, which were refined, leading to 18 studies in the final review data set. This review suggests that internet-based CBT is an effective strategy for reducing depressive symptoms in patients with comorbid depression and chronic diseases.