Purpose <p>The study aimed to support use of the Insomnia Daytime Symptoms and Impacts Questionnaire (IDSIQ) in clinical trials for patients with concomitant insomnia disorder and nocturia.</p> Methods <p>Eligible participants in this observational study were United States (US) residents aged ≥ 55 years who experienced self-reported symptoms reflecting the diagnostic criteria for insomnia disorder and nocturia (i.e., experienced ≥ 2 nocturnal voids per night within 30 days of screening). Concept elicitation (<i>n</i> = 10), confirmation of limited concepts (<i>n</i> = 5), and cognitive debriefing of the IDSIQ (<i>n</i> = 10) were conducted with 20 participants. A content analysis approach was used.</p> Results <p>Most participants in the overall sample were female (<i>n</i> = 13/20, 65%) and white (<i>n</i> = 17/20, 85%), with a mean age of 60.9 years. Based on concept elicitation, most participants (<i>n</i> = 9/10, 90%) experienced insomnia 5–7 nights per week and nocturia 7 nights per week. Participants identified impacts to their emotions, social activities, physical abilities, cognitive function, daily activities, work, and family for insomnia disorder and nocturia. These concepts were confirmed with the five additional interviews. Concept saturation for both disorders was achieved in all participants by the seventh concept elicitation interview. All cognitive interview participants (<i>n</i> = 10) understood the IDSIQ instructions, items, and response options.</p> Conclusions <p>Having concurrent insomnia disorder and nocturia is associated with daytime symptoms and impacts to functioning. All participants who were debriefed understood all IDSIQ items and response options. These findings suggest the IDSIQ is a content-valid instrument for use in clinical trials with patients with insomnia and comorbid nocturia.</p>