Introduction: Queuing is an event that is often encountered in everyday life. The purposes of conducting this research are to analyze the effectiveness of the queuing system that occurs during the service of ambulatory patient care and to examine whether the one-way queuing model (M/M/1) is still an affective model when serving ambulatory patient at the RSUD Dr. M.M Dunda Limboto, Gorontalo. The data used in this research is secondary data of ambulatory patients at the RSUD Dr. M.M Dunda Limboto, Gorontalo on February 2nd until 17th 2021 (during work days). Methods: An unobtrusive (non-reactive) analysis using the secondary data of ambulatory patients at RSUD Dr. M.M Dunda Limboto, Gorontalo. Results: The waiting time for ambulatory patient is 0.05 hour and the queue length formed is 3 patients, so there is no queue that significantly detrimental the patients at RSUD Dr. M.M Dunda Limboto, Gorontalo and the queuing system that applies at RSUD Dr. M.M Dunda Limboto, Gorontalo for ambulatory patients is an effective queuing system, where the server can serve all patients every day in a fairly short time using only one server. So, the M/M/1 system can still be used by RSUD Dr. M.M Dunda Limboto, Gorontalo.