ABSTRACTObjective: The primary objective of this study was to determine the quality of sleep among 12- hour shift-work nurses at the Baguio General Hospital using the Pittsburg Sleep Quality Index (PSQI). Methods: This was a preliminary cross-sectional study with a primary endpoint of assessing the sleep quality of the participants using the PSQI. The association of sleep quality with individual and work factors was also determined. Design:Cross - Sectional Study Setting:Tertiary Government Training Hospital  Patient:154 12-hour shiftwork nurses Results: The majority (88.96%) of the participants self-reported having poor sleep quality. Among the components of the PSQI, current shift was significantly associated with habitual sleep efficiency (Fisher exact test p < .049). No significant associations were found between demographic characteristics and PSQI Global score, with most respondents having poor sleep quality regardless of participant characteristics. Conclusion: Majority of nurses working in 12-hour shifts had poor sleep quality. Night shift nurses had higher habitual sleep efficiency scores compared to day shift nurses indicating that those working in the night shift had poorer habitual sleep efficiency.