The aim of this study was translating and exploring psychometric properties of Serbian Pittsburgh Sleep Quality Index (PSQI) in a sample of "good" and "bad" sleepers suffering from depression or obstructive sleep apnea (OSA). Formal translation and validation were performed on a sample of healthy controls, patients with untreated OSA, and with diagnosed major depressive disorder with evaluation of internal consistency, test–retest reliability, and construct and criterion validity. Controls and OSA subgroups were recruited from a larger sample of commercial drivers. One hundred and forty subjects, 84.3% male, 22–67 years old, were included. OSA subgroup had 59 subjects and depression subgroup had 40 subjects (22 females). Mean ± SD total PSQI was 3.5 ± 2.2 in controls, 4.9 ± 3.6 in OSA subjects, and 9.0 ± 4.9 in patients with depression. Cronbach’s α for total PSQI was 0.791. Subscale scores were significantly correlated to global PSQI in all subgroups. Intraclass correlation coefficient for global PSQI was 0.997 (p < .001). Epworth Sleepiness Scale score was significantly correlated to global PSQI ( = 0.333, p < .001). Three subgroups differed significantly in total PSQI and PSQI ≥ 5, even after adjustments for age and gender (p < .001). OSA patients had higher mean PSQI than controls but not significantly (p = .272). PSQI-reported sleep latency did not correlate with PSG-measured sleep latency (r = .130, p = .204). Total PSQI was significantly correlated to OSA severity ( = 0.261, p < .05). Serbian PSQI showed good internal consistency, test–retest reproducibility, and adequate construct and criterion validity, which supports further exploration of its use as a sleep quality screening tool in different target populations.