<p>The two species, the blue crab Callinectes sapidus and the Lessepsian species Portunus segnis, are considered among the most well-known invasive species of the Mediterranean coasts. These species represent both a threat and an opportunity. Indeed, the blue crab threatens marine biodiversity, causes disruption in local ecosystems, and jeopardizes the livelihoods of fishermen. From a circular economic perspective, several researchers have focused on the valorization of blue crab waste into high value bioproducts. Among these biomolecules are chitin and its derivative chitosan, which are used in several sectors such as medicine, food, agriculture, and environmental applications. These biomolecules are also effectively used to develop biodegradable and intelligent food biofilms with antioxidant and antimicrobial effects, thus offering an ecological alternative to conventional plastic use. Biochar, also produced from blue crab shells through the pyrolysis technique, has shown significant potential in wastewater purification and effluent treatment. This review aims to critically analyze recent advances in the valorization of blue crab shell waste into chitin, chitosan, and biochar, with a particular focus on technological maturity, environmental sustainability, and industrial scalability in the Mediterranean context integrating Technology Readiness Level (TRL) analysis with available Life Cycle Assessment (LCA) evidence. Relevant scientific publications were collected from major databases and comparatively analyzed in terms of process efficiency, functional performance, environmental impact, and technology readiness. The synthesis reveals that most chitin and chitosan extraction routes, including chemical, enzymatic, and green solvent approaches, remain at pilot or pre-industrial maturity (TRL 4–6), with persistent constraints related to energy demand, chemical consumption, wastewater management, and process integration. Biochar production via pyrolysis demonstrates promising adsorption performance for wastewater treatment and soil remediation but remains confined to laboratory and pre-pilot scales (TRL 4–5), with feedstock variability and scale-up optimization identified as key bottlenecks. Despite the growing interest in bioactive peptides, carotenoids, and smart biofilms, their industrial deployment is limited by insufficient techno-economic validation and scarce Mediterranean-specific LCA data. Overall, the principal gap identified for the Mediterranean region is the lack of harmonized environmental assessments and pilot-scale demonstrations under realistic operational conditions, limiting the transition toward industrial implementation. Priority research directions include the development of integrated marine biorefinery schemes, standardized LCA frameworks adapted to Mediterranean resources, optimization of low-impact extraction technologies, and strengthened industry–academia partnerships to validate scalable processing chains. These actions are essential to transform invasive blue crab biomass into a resilient and sustainable circular bioeconomy resource for Mediterranean coastal regions.</p>