Sport sponsorship on social media is a marketing promotional tool that has become increasingly popular. Further, the sport sponsorship spending is only expected to increase. Athletes are becoming brand ambassadors and communicators advertising products and brands on their social media channels. Collaborations between athletes and brands can be essential for both parties. Previous research has studied the concept of sport sponsorship´s influence on brand equity and sport sponsorship´s influence on social media engagement. However, to the best of the author's knowledge, no prior study has focused on how an individual's personality affects the perception of the brand personality of the sponsor brand, as well as the personality of the promoting athlete in the context of social media marketing. As culture differences have been reported to affect sport sponsoring, the decision was taken to focus on the Swedish market, which has not been studied before. Thus, the following research question was put forth: How do Swedish consumers perceive sport sponsorship on social media, and what are the effects of congruence? Through a mixed method approach the study aimed to answer the research question. The aim of the study was to develop a deeper understanding around sport sponsorship on the social media platform Instagram and how it affects consumers' attitude towards and perception of the brand acting as a sponsor. An online questionnaire was sent out to consumers within Generation Z as well as interviews were held with business practitioners to gain information from various perspectives. The findings of the study will give brand managers within the Swedish market insights into the consumers´ attitude towards sport sponsorship which will be of major importance when planning future activities within this area. The study is based on the theoretical framework centered on the Big 5 Personality Traits, Brand Personality and Congruency Theory. Results reveal that congruence between the consumer ́s personality traits and the athlete ́s personality traits as well as between the athlete´s personality traits and the brand's personality both have an impact on how consumers perceive the outcomes of sport sponsorship on social media. The outcomes studied were consumers´ perception of fit, consumers´ attitude towards the sport sponsorship, brand reputation and consumers perception of self-brand connection. Looking at the brand personality dimensions, sincerity is considered to be highly essential for a brand as it is this dimension alone that was shown to have an effect on how consumers view the sport sponsorship when it comes to overall fit, attitude, reputation and self-brand connection. An athlete, on the other hand, should be sought by being perceived as conscientious, as this trait is shown to have a positive impact on the congruence between the respondent and the athlete and influences the perceived overall fit, attitude, and self-brand connection. However, results also reveal that different athletes are perceived differently and thus the outcomes of the sport sponsorship, from the sponsoring brand´s perspective, may differ.