In this study, we employed institutional theory as a main framework and integrated it with concepts from diffusion of innovation and technology-organization-environment to examine a firm's intention to adopt software as a service. We operationalized our assessment of a firm's environmental pressures as mimetic, coercive and normative pressures and examined the moderating role of perceived technology complexity. We empirically tested our research model using data from 289 valid survey responses. The results provide support for the assertion that there are both significant direct and interaction effects that influence a firm's software as a service adoption intention. Most important was the significant interaction effects between mimetic pressure and perceived technology complexity. This suggests that the complex relationships proposed by institutional theory and diffusion of innovation help to describe how environmental pressures and perceived technology complexity combine to affect intention to adopt.