Many proposals to model service level agreements (SLAs) have been1 elaborated in order to automate different stages of the service lifecycle such as2 monitoring, implementation or deployment. All of them have been designed for3 computational services and are not well–suited for other types of services such4 as business process outsourcing (BPO) services. However, BPO services sup-5 ported by process–aware information systems could also benefit from modelling6 SLAs in tasks such as performance monitoring, human resource assignment or7 process configuration. In this paper, we identify the requirements for modelling8 such SLAs and detail how they can be faced by combining techniques used to9 model computational SLAs, business processes, and process performance indi-10 cators. Furthermore, our approach has been validated through the modelling of11 several real BPO SLAs.12