Serialisation technology was introduced to protect the pharmaceutical supply chain from infiltration by falsified and substandard medicines. The implementation of serialisation systems required a substantial investment by pharmaceutical manufacturers. This study investigated the impact of serialisation on the operational efficiency and productivity in Irish pharmaceutical sites. Ireland plays an important role in the global pharmaceutical manufacturing network. All of the top ten largest pharmaceutical companies have manufacturing operations in Ireland. A review of the literature showed only limited publications on the topic of serialisation, operational efficiency, and productivity, particularly in the Irish context. A research method was designed to assess the relationship between serialisation, operational efficiency, and productivity. The research consisted of a survey and interview process with 11 manufacturing sites in Ireland. Participating companies operated a total of 114 pack-lines, representing approximately 65% of the automated packing lines in the country. The research focused on measurements such operational equipment effectiveness (OEE), line availability, unit cost and cost per pack. The study revealed that serialisation had a negative impact on pack line OEE and line availability. The research found that serialisation had a negative impact on the unit cost of packaged pharmaceuticals. The study assessed the expected costs of serialisation with the actual costs experienced by manufacturers. The research found that the actual capital costs of serialisation were four times greater than the costs originally outlined by policymakers. The study identified a trend where Irish pharmaceutical sites are moving away smaller batch production and moving toward larger batches so as to gain greater efficiencies, The research also proposed the use of a serialisation depreciation factor ( 𝑆𝐷𝑓) as a method to determine the impact of serialisation on the cost of goods sold.