Due to the accelerating trend towards automation rate in industrial field, there is an increasing demand and requirement for industrial maintenance. Industrial companies started to outsource their maintenance services. Conventional outsourcing processes use contracts, which are usually uncertain in service level definition. Service Level Agreements (SLAs) are the key to solve this problem. SLAs are contractual agreements between a service provider and a customer, used to define a certain level of performance. This thesis takes an in-depth look at SLAs in outsourcing context and their emphasis on industrial maintenance. The goal of designing SLAs is to bridge the gap between service providers and customers. Literature shows that using SLAs in an outsourcing process improves the service quality. This is achieved by defining and focusing on key services, which are necessary to meet the company’s business requirements. SLAs are considered as a useful tool for service providers and customers to attain high quality as well as efficient service outcomes. SLAs help to simplify complex issues, reduce conflicts and improve communication. Well-defined Key Performance Indicators (KPIs) are important, because both partners need suitable KPIs to quantify service performance. Based on an intensive literature study on SLA, an 8-step SLA design process for industrial maintenance is demonstrated in this thesis. A structured questionnaire is developed in order to investigate the current situation of using SLAs for outsourcing maintenance services in industrial companies.