Outsourcing is one of the most successful and popular business concepts applied in numerous global organisations as a tool to enhance competitiveness. Managerial challenges are among the main issues involved in outsourcing laboratory diagnostic services which have a direct impact on successful treatment outcomes and hospital experience of patients. This study aimed to assess managerial activities and identify current challenges to provide insightful recommendations for outsourcing laboratory diagnostic services in private hospitals. Survey tools were handed out to hospital administrators and healthcare professionals in 85 private hospitals of Istanbul to evaluate managerial activities in outsourcing laboratory diagnostic services by analysing four important parameters: the extent of outsourcing, the decision-making process to outsource, the impact of outsourcing on private hospitals, and the future trend of outsourcing these services. The administrative, finance, healthcare professionals and legal teams are actively involved in the decision-making to outsource laboratory diagnostic services. The most recognisable benefits achieved were improved service quality level and risk reduction, meanwhile, cost reduction, improvement in customer satisfaction and service improvement impacted private hospitals in Istanbul. Also, service quality, company reputation, years of experience, price offered for the services and geographic distance from the outsourcing private hospital are very important criteria to evaluate potential laboratory diagnostic service providers. Outsourcing course of actions are required to guide hospital managers considering outsourcing laboratory diagnostic services for the first time, in outlining relevant information to identify, evaluate, engage and manage external providers of these services.