Seaweed farming and wild harvesting offer environmentally sustainable alternatives to conventional crop cultivation. Among red seaweeds, Grateloupia turuturu and Porphyra umbilicalis have gained attention due to their rich nutritional profiles and the presence of valuable bioactive compounds. Traditionally consumed in East Asia as vegetables, seasonings and sushi wrappings, their full potential remains underexplored, particularly regarding their detailed nutritional composition and functional bioactivities. In this study, proximate composition analyses were conducted following AOAC protocols, while mineral profiling was carried out using ICP-OES/ICP-MS. Hydroethanolic and aqueous seaweed extracts were prepared to assess acetylcholinesterase (AChE) inhibitory activity using Ellman’s assay. Additionally, the immunostimulatory effect of seaweed extracts was evaluated in RAW 264.7 macrophages through the colorimetric measurement of ^•NO production. Dietary fibre stood out as the predominant nutritional component (50% dw of P. umbilicalis). G. turuturu exhibited greater ash content (30.98% dw) than P. umbilicalis (21.61% dw), but a lower protein level (20.16% vs. 22.32% dw, respectively). Both seaweeds showed residual lipid levels (1.52 % dw). Sodium, zinc, iron, and iodine were identified as the most relevant minerals in both species. All extracts inhibited AChE activity by more than 20%, with the decoction of P. umbilicalis reaching nearly 50% inhibition. For immunostimulation, the decoction of G. turuturu at 0.20 mg/mL produced the highest increase in ^•NO levels, 153.17%. Through a literature-anchored review, when benchmarked against commonly consumed terrestrial plants with a high environmental footprint—namely wheat, white rice and tomatoes—G. turuturu and P. umbilicalis showed higher levels of protein, fibre, and minerals. Unlike conventional agricultural crops, these seaweeds can grow without the need for land, freshwater or chemicals, and display great bioactive potential. These results reinforce the potential of G. turuturu and P. umbilicalis as promising functional foods, highlighting their relevance as sustainable, nutrient-rich resources with promising neuroprotective and immunomodulatory properties.