This research aims to study the impact of custom on the lease contract generally and its contemporary practices in particular, together with the shari’aah rulings (al-ahkam) on the applications of the lease contract in terms of formation and effects. The research is presented in five chapters; the first chapter deals with the introductory and methodological issues, and the second touches the definition of custom, its types, renewabilty, legitimacy, conditions and importance. The third chapter is about the definition of lease, its pillars, its contemporary forms, its legitimacy in general and its conditions. The fourth chapter deals with the impact of the custom in rulings regarding the applications of the lease contract in terms of formation. In this chapter the impact of custom in options (al-khiyarat) and forms of leasing are discussed. The final chapter of the research indicates the impact of custom on the rulings of the applications of the contemporary lease contract. It explains the impact of custom in the shari’ah legal rulings (al-ahkam) of the tenor of lease, its utility, rental and possession. It also explains the impact of the custom in the ownership of usufruct, the rights and limits of the utility and its guarantee. The methodology used in this research is the inductive approach by which scientific materials are collected related to the custom and its impact on the classical as well as the contemporary lease contract. The research also used analytical method in order to analyse the opinions of the shari'ah scholars on the lease. The research found that the valid custom plays a significant role in establishing the contracts of lease in all its types, whether it is the contract of lease regarding the usufructs or the labour. All forms of lease on their formation and consequenses shall have their impact as long as they comply with the conditions of the valid shari’ah custom.