Mizaj concept in the Unani system of medicine is a wide area of research. Mizaj theory has its roots in the ancient four humors theory. It was the Greek physician Buqrat (Hippocrates 460-370 BC) who systematized and developed it into a medical theory. He believed certain human moods, emotions, and behaviors were caused by body fluids (called “Humor”): blood, yellow bile, black bile, and phlegm. So, it is necessary to find out its relationship with physical fitness which may be influenced by individual mizaj (body type) and it can be considered as a decisive advantage to selecting an appropriate exercise for each athlete. Research in this area is very scanty and inconclusive, therefore the participants of young age and clinically healthy have been chosen as the subject of study. The objective of the present study is to find out the nature of mizaj (body type) with physical fitness. The sample of the present study was drawn from Ayurvedic and Unani tibbia college students, both boys and girls. In the present study, mizaj was assessed by using a mizaj assessment questionnaire based on ten classical parameters described in the Unani classical literature category, and physical fitness was determined by physical fitness index(PFI) using a modified Harvard step bench test. Analysis of data in the current study was done by calculating the mean, standard deviation, and one-way ANOVA in SPSS 22.0 software for all the factors of mizaj and physical fitness. It is observed that PFI, is highest in people having Damvi Mizaj and lowest in people having saudavi Mizaj and it is in concordance with the experimental hypothesis of this research work. From this study, it is clear that a possible correlation between PFI and Mizaj certainly does exist. After that, PFI could be considered as one of the diagnostic indices of temperament.