This paper describes the key elements of Pashtunwali and the manifestation of Pashtun nationalism, especially in Pakistan. This study on Pashtun nationalism finds that Pashtunwali is a centuries-old primordial customary code of life and it is important in the context of nationalism as it strengthens the sentiments and feelings of closeness and affinity; central to the phenomenon of nationalism, among the Pashtuns. This paper also highlights two different aspects of Pashtun nationalism in Pakistan. In the formative phase of Pakistans independence, the stance of Pashtun nationalists was more inclined towards the idea of a separate state for the Pashtuns. However, as a result of various factors; including state policies, currently the manifestation of Pashtun nationalism has adopted the internal dimension of highlighting and struggling for the rights of the Pashtuns in the ambit of the Pakistani constitution and by remaining an integral and constitutional part of the country.