The efficiency of engine combustion is strongly dependent on fuel atomization and spray processes which in turn are greatly influenced by nozzle internal geometry and parameter like air to liquid ratio (ALR). Modern engines employ different geometrically designed nozzles. It is crucial to characterize the effect of the internal geometry of the nozzle and ALR on atomization characteristics. In this study, the effects of geometric parameters of the pressure-swirl duplex nozzle and ALR on the spray characteristics of Jet A-1 fuel were investigated. Two different shaped pilot nozzles and two different shaped main nozzles were used. The analysis of spray characteristics was done by using particle image velocimetry (PIV) system and phase Doppler anemometry (PDA) system. Spray cone angle, Sauter mean diameter (SMD) distribution and weighted mean SMD (WMSMD) were analyzed. In the case of the effect of the internal geometry of the nozzle, the results show that when main and pilot nozzle work together, it produces a higher spray cone angle compared to the pilot nozzle alone. Cone-shaped pilot nozzle tip exhibits better atomization characteristic than flat shaped pilot nozzle tip. Combined main and pilot nozzle with counter-rotating flow provides smaller droplets and higher spray cone angle than co-rotating flow configuration. In the case of the effect of ALR, a decreasing trend in the spray cone angle is found with increasing ALR. Moreover, WMSMD increases with increasing ALR up to 1.16, but thereafter, it decreases again.