Patients seeking transdiagnostic internet-delivered cognitive behavior therapy (T-ICBT) for anxiety or depression often have sleep difficulties. A brief resource that includes sleep psychoeducation and strategies for improving sleep (e.g., stimulus control and sleep restriction) may address comorbid insomnia without the need for an insomnia-specific ICBT course. This observational study explored patient use and feedback of a brief sleep resource available to all patients (N = 763) enrolled in an 8-week T-ICBT course. Overall, 30.1% of patients (n = 230) reviewed the resource and were older, more engaged with the ICBT course (i.e., more likely to complete the program, more logins, and greater number of days enrolled in the course) and had higher pretreatment insomnia symptoms than those who did not review the resource. Resource reviewers did not report larger improvements in symptoms of insomnia than non-reviewers, even among patients with clinical levels of insomnia, and average insomnia levels remained above the clinical cutoff at posttreatment. While patients were satisfied with the resource and it was beneficial to some patients, more research is needed to further explore how it may be integrated into T-ICBT and how therapists can encourage the use of the resource among patients who may benefit from the resource.