© 2016 John Wiley & Sons Ltd.Aim: This study was conducted in an attempt to examine the number and duration of interruptions during the medication preparation process and to identify the factors causing these interruptions. Background: Interruptions during the medication preparation process can cause medication errors owing to nurses' lack of attention. Method: A descriptive study was conducted at the Internal Diseases and General Surgery services of a university hospital between 15 June 2012 and 30 July 2012. The data were collected using the 'Observation Form of Preparing Medication.' Result: A total of 122 observations were made in the study. It was found that there was an interruption during the process of preparing medication in 95.9% of observations. The average number (±SD) of interruptions was 5.8 ± 4. The individuals causing the interruption during medication preparation were primarily nurses working in the same service. Receiving from or giving materials to the treatment room were the main reasons for the interruptions. Conclusion: This study found a very high interruption rate during the process of preparing medications. Implications for nursing management: As interruptions during medication preparation can cause medical errors, in-service teaching should be provided to raise awareness for this important issue. The findings of the study can be useful for enhancing the conditions of the physical environment, separating the treatment rooms and using the treatment rooms only for preparing medication.