Compare the circadian trajectory of diuresis between nocturnal polyuria (NP) patients with versus without identifiable contributory comorbidities. Retrospective analysis of frequency-volume charts from male patients with clinically-significant nocturia (≥2 nocturnal voids) and NP (defined by nocturnal urine production [NUP] ≥90 mL/hour or nocturnal polyuria index [NPi] ≥0.33). Patients with NP and chronic kidney disease, congestive heart failure, and/or undertreated obstructive sleep apnea (OSA) were deemed to have secondary NP. Nocturnal polyuria syndrome (NPS) was defined as NP without edema, loop diuretic use, or the aforementioned conditions. Patients with diabetes insipidus or OSA with appropriate continuous positive airway pressure utilization were excluded. The timing and volumes of nocturnal voids were used to derive "early" and "late" nocturnal diuresis rates (mL/hour of urine produced before and after the first nocturnal awakening, respectively). The likelihood of an early peak nocturnal diuresis rate (ie, early >late nocturnal diuresis rate) was compared between patients with NPS versus secondary NP using both a crude and adjusted odds ratio. The likelihood of an early peak nocturnal diuresis rate in patients with NPS compared with secondary NP was 2.58 (1.05-6.31) at NUP ≥ 90 mL/hour and 1.96 (0.87-4.42) at NPi ≥ 0.33 on crude analysis, and 2.44 (0.96-6.24) and 1.93 (0.83-4.48) after adjustment, respectively. A peak early nocturnal diuresis rate was significantly more likely in patients with NPS at NUP ≥ 90 mL/hour, with similar odds ratios at NPi ≥ 0.33 and following adjustment. Delineating nocturic patients by NP subgroup may facilitate more individualized management. Many people have to wake up to urinate because they produce too much urine at night-a condition known as "nocturnal polyuria." Nocturnal polyuria might be caused by drinking too much fluid, other behavioral factors, or conditions that make your body hold on to too much fluid, like heart disease, kidney disease, and sleep apnea. In cases of nocturnal polyuria where no clear cause can be identified, it is thought that patients may suffer from a deficiency in nighttime vasopressin, a hormone that plays a key role in how much urine you produce. In this study, we compared the pattern of nighttime urine production in patients with different causes of nocturnal polyuria, which may lead to more personalized treatment options for patients with this condition.