Abstract Objective Sleep is part of a healthy lifestyle and in adults with diabetes, inadequate sleep is associated with risks of developing complications. The objective was to compare beliefs about healthy sleep habits (HSHs) in adults with versus without diabetes based on the Reasoned Action Approach. Methods A total of 56 adults with and 98 without diabetes answered open-ended questions regarding their beliefs about: avoiding screen use in bed; having a regular sleep schedule; or avoiding caffeine, alcohol, and cigarettes before bedtime. A qualitative content analysis was used to identify the most important beliefs, similarities, and differences between both groups. Results Both groups reported that adopting HSHs could improve sleep. Having a regular sleep schedule was perceived to facilitate diabetes management in adults with diabetes. Negative consequences specific to adopting each HSH were identified in both groups. Adopting HSHs was associated with mainly negative emotions (e.g., stress, anxiety, fear) in both groups. Avoiding screen use in bed was associated with anxiety of not knowing blood glucose levels at night in adults with diabetes. Partners, parents, and friends were considered the most important individuals who would approve of adopting HSHs, but they were often perceived as unlikely to adopt HSHs themselves in both groups. Adults with diabetes perceived more barriers to adopting HSHs. Facilitating factors for both groups included removing triggers of unhealthy sleep habits, behavior substitution, using reminders, time management, and social support. Discussion These beliefs can guide the development of behavioral sleep interventions, including interventions specifically for adults with diabetes.