Objective: Vascular function serves as an early indicator of cardiovascular (CV) risk. The intake of n-3 polyunsaturated fatty acids (PUFAs) has been reported to improve arterial properties and reduce CV risk, but evidence in healthy individuals remains limited. This study investigated the effects of consuming n-3 PUFAs-enriched chicken meat on vascular reactivity at both microvascular and macrovascular levels in healthy young adults. Materials and Methods: In this placebo-controlled, double-blind, randomized interventional trial (ClinicalTrials.gov: NCT05725486), 39 participants (aged 20–26 years) were assigned to either the Control group (n = 20; approximately 118 mg n-3 PUFAs/day) or the n-3 PUFA group (n = 19; approximately 1500 mg n-3 PUFAs/day) for three weeks. Microvascular reactivity was assessed via post-occlusive reactive hyperemia (PORH), acetylcholine-induced dilation (AChID), local thermal hyperemia (LTH), and sodium nitroprusside-induced (SNPID) responses. Macrovascular reactivity was measured by brachial artery flow-mediated dilation (FMD) and nitroglycerine-mediated dilation (NTG-MD). Body composition and blood pressure (BP) were recorded before and after the intervention. Results: Both microvascular (PORH, AChID, and LTH) and macrovascular (FMD) endothelium-dependent vasodilation increased in the n-3 PUFAs group following the dietary protocol compared to the Control group. Conversely, the three-week dietary intervention did not influence endothelium-independent dilation in either the microvasculature (SNPID) or macrovasculature (NTG-MD) within the groups compared to baseline, nor were any differences observed between the groups. No significant changes were noted in BP or body composition after either diet. Conclusions: In healthy young adults, consuming the n-3 PUFAs-enriched chicken meat for three weeks improved endothelium-dependent vasodilation in both micro- and macrocirculation, without affecting endothelium-independent responses. These findings suggest that dietary n-3 PUFA intake may provide vascular benefits even in healthy, disease-free individuals at rest.