As medication safety is a foremost goal of patient safety, the adoption of bar-code medication administration can help nurses ensure safe medication administration. The aims of the study were to explore the impact on nursing activity patterns of using this device and to understand the nurses' usage of this technology. The data collection was conducted in a medical center in northern Taiwan using work sampling observation and qualitative interviews. A total of 4940 observations were conducted on two groups of nurses who did or did not use the device, and six nurses were interviewed using a semistructured interview guide. The results showed that the nurses who used this device spent less time on medication-related activities and more on indirect care and unit-related activities, especially on the day and night shifts. Three themes were identified from the follow-up interviews: facilitating nursing workflow, improving medication safety, and encountering operational difficulties. Although the technology use could divert the nurses' practice patterns from medication-related activities to indirect care and unit-related activities, their direct care was not compromised. In addition, although the bar-code medication administration use could improve workflow and patient safety, hardware sufficiency and system functionality deserve more attention in the technology adoption process.