The need for cognition has consistently been proven to be correlated to academic success, but the mechanisms of that relationship are not fully explained yet. One possibility is that the need for cognition affects academic success via study-related flow. However, an important factor in any research, including the need for cognition, are valid instruments. The need for cognition is often assessed with the Short Need for Cognition Scale, but there is a lack of data on its validity in Croatian samples. The aim of this research is to test whether study-related flow mediates the relationship between the need for cognition and academic success and to validate the Croatian version of the Short Need for Cognition Scale. Research was conducted via an online survey that gathered information about participants’ need for cognition, study-related flow, personality traits, and several indicators of academic success. The survey was fully filled out by 545 students from all over Croatia. Confirmatory factor analysis determined that the factor structure of the Short Need for Cognition Scale is best described by the general factor of the need for cognition and the method factor for reverse scored items. The Scale demonstrated metric invariance - identical factor structure and factor saturations across gender. The established relationships of the Scale with personality traits and gender are partially in line with expectations based on previous research, apart from the unexpected association with extraversion and agreeableness and the lack of association with conscientiousness. Lastly, full mediation of study-related flow on the relationship between the need for cognition and academic success was established. In conclusion, the Croatian version of the Short Scale of Need for Cognition shows good psychometric characteristics and can be used in the Croatian context. In addition, this research demonstrates the importance of study-related flow and the need for cognition in the academic context and encourages future research that would further strengthen the knowledge about the need for cognition in the academic setting.