Prior studies indicate nocturnal wakefulness is associated with suicide, while morning wakefulness is linked to reduced suicidal ideation. These relationships, however, may be confounded by sociodemographic factors. Therefore, this study investigated whether timing of wakefulness was associated with suicidal ideation in a nationally representative sample. Data were collected from the US National Health and Nutrition Examination Survey for the years 2015 to 2018, resulting in a final sample of 10,166 participants (51.1% female) with complete data available on suicidal ideation status, time to bed, and time out of bed. Population-weighted logistic regression models estimated the associations between time spent out of bed (ie, being awake) and suicidal ideation. A total of 385 survey participants (47.5% female) reported suicidal ideation in the past 2 weeks for a population-weighted prevalence of 3.37% (95% CI, 2.85%-3.87%). Wakefulness between 11:00 pm and 5:00 am was associated with suicidal ideation (OR = 1.16; 95% CI, 1.08-1.24 per hour), even after adjustment for sociodemographic factors and symptoms of sleep disorders, but not after adjustment for the severity of depression symptoms. Conversely, wakefulness between 5:00 am and 11:00 am was associated with reduced odds of suicidal ideation (OR = 0.77; 95% CI, 0.70-0.85 per hour) in all models. Individuals who spent more time awake at night were more likely to have recent suicidal ideation, while the opposite was true for those with more time spent awake in the morning. Moreover, these associations were independent of sociodemographic factors and thus not confounded by varying rates of suicidal ideation in different populations.