whether or not perfectionism is a healthy personality characteristic is a topic of much debate among researchers (flett & hewitt, 2005). one way to investigate this is to differentiate how “healthy” or “unhealthy” perfectionists perceive achievement demand s. during their athletic careers, athletes experience the achievement demands of transitioning to higher levels of performance. one of the most demanding of these transitions is the junior to senior sport transition. as of yet, there is no research regarding how perfectionists experience and perceive the junior to senior sport transition. therefore, the purpose of this study was to explore how healthy and unhealthy perfectionist athletes experience the transition from junior to senior sport. this study employed a sequential mixed method design. in step 1, 27 current and former members of a high-performance cross-country skiing training program completed the sport multidimensional perfectionism scale-2 (sport-mps-2: gotwals & dunn, 2009), and coaches rated the athletes’ respective levels of perfectionistic strivings and perfectionistic concerns. using intra-sample and inter-sample criteria scores for the sport-mps-2, and the coaches’ ratings, the athletes were designated as either healthy perfectionists, unhealthy perfectionists, or non-perfectionists. however, these characterizations did not yield a sufficient number of participants to compare healthy and unhealthy perfectionists. therefore, the focus of the study was redirected toward athletes with high perfectionistic strivings, which is one of the overarching dimensions of perfectionism (stoeber & otto, 2006). in step 2, using an open-ended interview guide, six athletes who met the criteria of high perfectionistic strivings were interviewed regarding their respective experiences and perceptions of the junior to senior sport transition. inductive thematic analysis was used to analyze the qualitative data. eight themes emerged from the analysis: balancing priorities, expectations as national training program skiers, overthinking and overdoing, team dynamics, competition, poor performance and related emotions, negative effects of training, and hindsight. these themes are contextualized within the stress process, the athletic career transition literature, and the perfectionism literature. the implication of this study is that perfectionistic strivings should be accounted for during the junior to senior sport transition.