The effects of long-term sports sponsor relationships on purchase intentions of supporters have not been studied before and therefore the aim of this study is to investigate this particular phenomenon. The focus is on three different lengths of sponsor relationships to draw further conclusions. Additionally, how the purchase intentions of supporters are formulated and where the differences come from is explored. Both primary and secondary data were gathered in order to answer the research question. Based on the secondary data gathered related to the topic a survey was conducted to gather primary data. Answers to the survey were collected from the supporters of three case teams. Responses to the survey were analyzed using the quantitative method and the three teams were compared to each other using a theory presented in the literature review to find results. It was found that supporters of teams with longer relationships were more familiar with the existing sponsor relationship. The results showed that when the sponsor relationship is longer the supporters’ purchase intentions are higher. There was also an increase found in the overall opinions of supporters towards the sponsor’s product over time. When the sponsor relationship becomes longer over time supporters start having more opinions towards the product leading to higher purchase intention.