Atrial fibrillation (AF) is the most common cardiac arrhythmia and increases stroke risk and reduces quality of life. Left atrial catheter ablation (LACA) restores sinus rhythm by targeting abnormal electrical sources. Pulmonary vein isolation (PVI) is the most common approach, while left atrial appendage electrical isolation (LAAEI) is used selectively but may raise thrombus risk. Computational fluid dynamics (CFD) has been used to model thrombogenesis during LACA, but the relationship between blood temperature and coagulation is yet to be modelled. We performed twenty-nine simulations coupling CFD with heat transfer during PVI and related thrombogenesis in the left atrium. These included PVI at 80 °C and 60 °C, LAAEI at 80 °C, and ablation sites at increasing distances from the LAA. Experimental data linking temperature and coagulation were used to calibrate a thermal exposure model, alongside transport and reaction equations for coagulation proteins, including fibrin. At 80 °C, PVI produced variable fibrin formation across the PVs, with no significant differences between PVs or correlation with PV velocity. At 60 °C, fibrin remained below the thrombus threshold, and fibrin at 80 °C was significantly greater (p = 1.91×10⁻⁶). Including LAAEI produced a significant overall difference in fibrin among sites, but no pairwise differences remained after correction. Fibrin decreased with increasing distance from the LAA orifice, showing a significant negative correlation after three and twelve cycles. These results highlight risks of temperature-dependent thrombogenesis and suggest reduced thrombus risk with more distant ablation from the LAA.