In a prospective study, CT angiography (CTA) was used to assess changes in carotid perivascular fat attenuation as a surrogate marker of local vascular inflammation in 70 patients with severe unilateral carotid artery stenosis who underwent either carotid endarterectomy (CEA) or carotid artery stenting (CAS). Images were obtained before and after CEA or CAS of both the stenotic and contralateral non-stenotic sides. On the stenotic side, median carotid perivascular fat attenuation showed a small but significant change (from −60 HU [IQR −66 to −57] pre-treatment to −61 HU [IQR −66 to −56] post-treatment (P = 0.046). A more significant change in perivascular fat attenuation was observed following CEA (P = 0.006) as opposed to CAS (P = 0.103). Post-procedural perivascular fat attenuation on the treated side correlated moderately with treatment occurrence (Spearman ρ = 0.403, P = 0.003). In addition, perivascular fat attenuation measured on the untreated side correlated with stenosis severity both before (ρ = 0.328, P = 0.007) and after treatment (ρ = 0.271, P = 0.027). These findings support the capability of CTA-derived perivascular fat attenuation to reflect perivascular inflammatory response and suggest that CEA, more than CAS, is associated with increased local inflammation detectable on CT imaging.