Backgrounds: Early identification of clinical conditions and proper treatment to dengue patients is essential to prevent the development of more severe condition. This can lead to shorter length of stay and lower cost of patient care in hospitals. The objective of this study was to determine the effect of fever duration before hospitalization and hemoconcentration to length of stay of dengue patients. Methods: A cross-sectional study conducted by random sampling on the medical records of dengue patients hospitalized in RSPI Prof. Dr. Sulianti Saroso period January 2014-December 2015. Multivariate analyzes were performed with Cox regression. Results: There were 153 samples of dengue patient's medical record for analysis, 21.6% of them were hospitalized over 6 days. Duration of fever before hospitalization and hemoconcentration were significant to length of stay more than 6 days. Subjects with duration of fever for 3 days [aRR = 0.38; P = 0.024] and more than 3 days before hospitalization [aRR = 0.27; P = 0.000] were significant to length of stay more than 6 days. Subjects with hemoconcentration had higher risk by 1,8 times to length of stay more than 6 days [aRR = 1.84; P = 0.042]. Conclusion: Fever duration for 3 days, for more than 3 days before hospitalization, and hemoconcentration in dengue patients were significantly related to length of stay more than 6 days.