Hydraulic and internal flow characteristics of swirling superheated liquid jets of aviation fuel were investigated experimentally and numerically. Liquid hydrocarbon was heated to close to 573 K (300 °C) using an induction heater at an upstream pressure of up to 1.1 MPa and discharged to atmospheric downstream pressure conditions through a simplex pressure-swirl nozzle. Hydraulic characterization in terms of fuel temperature was carried out by introducing the discharge coefficient Cd, and the macroscopic internal flow characteristics were correlated with Reynolds number and cavitation numbers. As compared with the plain orifice injector configuration, with the pressure swirl injector the normalized Cd trend with respect to fuel injection temperature Tinj increases more with increasing Tinj until Tinj reaches the boiling point, and the resultant higher normalized Cd at the boiling point decreases faster as Tinj increases further above the boiling point. The CFD analysis of the swirling high temperature liquid jets shows that for cases of Tinj above the boiling point, the internal flow of the swirl injector becomes independent of the ambient (downstream) pressure. This implies that the swirl flow has reached the mass flow choking, or critical cavitation condition. Furthermore, the relatively scaled velocity and the normalized pressure P/Psat distributions of the swirl injector are found to converge to an almost identical shape when Tinj exceeds the boiling point, irrespective of ΔPs and Tinj. Distinct evidence of the choked cavitation of the swirling high temperature liquid jets is observed in the relationship between the mass flow rate and (Pinj − Psat)1/2, which shows that the mass flow choking of the swirling high temperature liquid jets is initiated as soon as the fuel injection temperature increases past the boiling point, and the effect of the choked cavitation represented by the decrease of the mass flow rate becomes stronger as Tinj increases further. Finally, the clear dependence of Cd on cavitation number suggests that cavitation dominates the Cd characteristics of the high temperature fuel injection for the swirl injector when Tinj increases past the boiling point, and, therefore, the degree of thermal cavitation of the swirling superheated liquid jets is nicely represented by the cavitation numbers.