Health Management Information System (HMIS) has sub system under HIS is specially designed to assist the management and planning of health programmes opposed to delivery of care that provides decentralized decision making and planning. However, decentralized informational management is at infancy stage in Ethiopia. Hence, to ensure the effective and efficient utilization of a system, periodic assessment becomes imperative at this juncture. The study aims in assessing utilization of HMIS at Public Health Centers in Addis Ababa. Institution based cross sectional quantitative and qualitative study was conducted from July to September 2011. The sample size was calculated using single population proportion formula and a total of 416 health professionals were included. Frequencies, proportion and summary statistics were used to describe the study population in relation to relevant variables. Bivariate and multivariate analyses were also be carried out to see the effect of each independent variable on the dependent variable. 416 respondents respond to the questionnaire with 98% response rate. The current utilization rate of HMIS at health centers were about 41.7%. The total outcomes of the generated routine data were compiled using tally sheet, registers, and reports, and in combination of these formats. The combined utilization of the mentioned formats constituted 199 (48.8%). The odds ratio result indicated that the provisions of technical supports, presence of computers, generated data at department level and practice of conversion of data into information enhanced the utilization of HMIS (AOR=1.69, 95%CI:1.09-2.63), (AOR=2.08, 95%CI:1.29-3.35) (AOR=2.78, 95%CI:1.65 -4.68), and (AOR=3.44, 95%CI:(1.82-6.51) respectively.