Despite the exponential growth in internet usage for personal communication over the last 10 years (Madden & Zickuhr, 2011) little is known of the online interpersonal persuasion process. Whilst some psychological research has been undertaken in this area, the findings are somewhat contradictory (e.g. Di Blasio & Milani, 2008; Murphy, Long, Holleran, & Esterly, 2003). These studies also fail to give consideration to cues used in online persuasive interactions due to the absence of paralinguistic cues. Further, the extant research in this domain has not explicitly examined the persuasion process in terms of a theoretical model. This thesis aims to address these issues and provide a foundation from which future research can be based. This thesis comprises two studies. The first study examined participants’ reactions to anonymous persuasive requests. These requests were presented using three situational contexts, each of which elicited different self-interest motivations (i.e. social, learning, and political). It also compared participants’ reactions to these contexts across three different communication modes both online and offline (i.e. instant messaging, email, and face to face). Language cues (i.e. language power and emotion) contained in the messages presented were also manipulated. The findings from this study show that in anonymous interactions communication mode does not affect compliance decisions. Instead, individuals are sensitive to situational context in online interactions and they process information in accordance with their self-interest motivations. Further, it was also found that, despite the anonymity, individuals are able to engage in impression formation by using the available cues and utilise these impressions when making compliance decisions. In response to these findings, Study 2 examined the effect of prior information in online interpersonal persuasive interactions and found that this information influences message evaluations over and above those in anonymous interactions. This study also examined the persuasion process in terms of a theoretical model finding that individuals engage in hypothesis-testing utilising all the information they perceive to be relevant to a compliance decision. Thus, it was concluded that Kruglanski and Thompson’s (1999) unimodel of persuasion provides the best explanation for online interpersonal persuasion processes. The findings from this thesis provide a broad foundation from which to base future research. They demonstrate that context is important in online communication and affects compliance decisions. They also show that cues are attended to in online interactions and are used in the evaluation process as they provide relevant evidence from which to base a compliance decision. From the findings of this thesis a model of the interpersonal persuasion process is proposed.