Purpose <p>Fibromyalgia is common in type 2 diabetes (T2D). However, its prevalence and impact on T2D-related complications, particularly in large-scale settings, remain unclear. This study estimated the prevalence of fibromyalgia in T2D and its impact on T2D-related complications.</p> Methods <p>This retrospective cohort study used TriNetX data. We defined the T2D cohort by using <i>International Classification of Diseases</i>,<i> Tenth Revision</i> codes, and we estimated the prevalence of fibromyalgia in this cohort for the period between June 1, 2019, and June 1, 2024. We defined patients with T2D and fibromyalgia as Cohort 1 and patients with T2D but without fibromyalgia as Cohort 2. We then performed 1:1 propensity score matching between the two cohorts. In July 2024, we conducted risk analyses (measured through odds ratios) and survival analyses by using the built-in algorithms on the TriNetX platform.</p> Results <p>The overall prevalence of fibromyalgia was 4.03% in patients with T2D (6.16% and 1.65% in women and men, respectively). Patients aged 45–49 and 50–54 years had the highest prevalence of fibromyalgia. Cohort 1 exhibited approximately 20% to 90% higher cumulative odds of T2D-related complications compared with Cohort 2. These complications included cardiovascular disease, major adverse cardiac events, ischemic heart disease, coma, ophthalmic disease, nephropathy, neuropathy, and foot ulcers. Additionally, the instantaneous risk of these complications, with the exception of nephropathy, was higher in Cohort 1 than in Cohort 2.</p> Conclusion <p>This study estimated the prevalence of fibromyalgia in T2D and indicated that fibromyalgia might augment T2D-related complications. </p>