Theoretical models of person perception (e.g., the Schematic Model of Person Perception, Warr & Knapper, 1968) have conceptualised the range of stimuli a perceiver will use to form an impression of a target and their subsequent responses to these stimuli. The main aim of this thesis was to examine person perception in sports interactions. Specifically, the aims were to examine a) the stimuli sports performers attend to b) the attributive, expectancy and affective responses sports performers develop to initial impressions c) the influence of initial impressions on attributions for an opponent's performance and d) the influence of initial impressions on a performer's attention and competitive sports performance. Study one of this thesis presents qualitative research highlighting the range of stimuli available to tennis performers, common attributive responses and reported impacts of an impression on a performer's state, expectations and performance. Study two provides empirical support for the suggestion that performers experience attributive and expectancy responses to their opponents' body language. Specifically, when a potential opponent displayed positive body language, participants rated both episodic and dispositional judgements significantly more positively than when negative body language was displayed. When the potential opponent's body language was positive participants' expectations of the opponent's performance, their own performance and the demands of a match were rated as significantly greater than when negative body language was displayed. When the potential opponent's body language was positive participants' expectations for the overall outcome of a match were rated significantly lower than when negative body language was displayed. Study three shows that, despite performance specific stimuli becoming available later in the interaction, an initial impression influences how an opponent's performance is judged. Specifically, when a potential opponent displayed positive body language his technique, power and movement were rated significantly higher than when negative body language was displayed. Study three also highlights how person perception can influence how a performer's attributes his or her opponent's performance. Study three showed that when a potential opponent displayed positive body language a successful performance was attributed to greater levels of skill and when negative body language was displayed a successful performance was attributed to luck. Study four demonstrates that an opponent's prior performance record can prompt a significant affective response, with participants given stimuli showing their opponent had won all previous competitions reporting significantly greater levels of cognitive anxiety. Participants given stimuli showing their opponent had won all previous competitions of a golf putting game also showed a significant decrease in competition scores from a baseline measure, indicating that an initial impression of an opponent influenced the perceiver's performance of a fine motor skill. The opponent's prior performance was seen to influence the amount of time a performer spends attending to their opponent's stimuli, with participants given no prior performance information attending to their opponent's subsequent neutral stimuli for significantly longer durations than participants provided with prior performance stimuli. Overall the research presented in this thesis provides support for the use of the Schematic Model of Person Perception (Warr & Knapper, 1968) as a theoretical basis of investigation in sports-specific person perception research. Initial support is given to the proposal that person perception can be a significant factor in a performer's judgements of an opponent, expectations, affective state and attentional style prior to performing.