Treatment of complex intracranial aneurysms represents a challenge for neurosurgeons and neuroradiologists. Various surgical procedures are available for complex aneurysms, such as selective clipping, coiling, and other endovascular techniques such as flow-diverters. However, in some patients, these surgical procedures are not feasible due to the complexity of the aneurysm, its size, shape, wall calcification, incorporation of major arteries in the aneurysm sac, accessibility, and flow characteristics. Some complex aneurysms can be handled with bypass surgery. The present study performs computational fluid dynamics-based simulations as per extracted computed tomography (CT)-angio data before and after the bypass surgery. To simulate realistic flow conditions, patient-specific blood flow rate at the inlet of ICA aneurysm models were measured using transcranial Doppler (TCD) and applied in the form of a velocity waveform using a Fourier Series. The various hemodynamic indicators—time-averaged wall shear stress, oscillatory shear index (OSI), and relative residence time (RRT)—are introduced to quantify flow dynamics. During the systolic phase, blood impinges the dome of the aneurysm in the pre-surgery interval, while in the post-surgery at the instance of t=0, the flow reversal induced low-velocity values in the aneurysm sac causes a permanent static zone. Since the post-surgery at t=3 months results in flow stasis, the aneurysm gets partially thrombosed gradually. The flow features for the post-surgery at t=3 months represent streamlined flow in the aneurysm. One of the hemodynamic parameters, i.e., Relative Residence Time (RRT), is computed along the curve on the aneurysm periphery for all three surgical intervals. The RRT value is substantially higher for the post-surgery at t=0 compared to the pre-surgery interval. The low velocity and elevated RRT may induce partial aneurysm thrombosis, thereby achieving a clinical cure.