Seaweeds or macroalgae are dominant groups of marine autotrophic organisms distributed across vast stretches of the oceanic surface. Macroalgae, with their wide range and types, have contributed immensely towards humanity in different forms such as cleansing the ecosystem, food, feeders, traditional medicines, modern pharmaceutical drugs, bioplastics, nutraceutical food products, etc. Bioactive compounds like fucoidan, alginate, carrageenan, agar, and ulvan are some of the valuable input from seaweeds. Advancements in biotechnological techniques and extraction processes, such as microwave-assisted extraction, ultrasound-assisted extraction, pressurized solvent extraction, supercritical fluid extraction, etc., have further enabled us to reach out to the untamed bioactive metabolites of seaweeds. Algal biomasses being a storehouse of diverse groups of compounds, their role as unconventional and promising carbon or feedstock sources remains underexplored. Through the study, we attempt to explore unconventional biological approaches like bio-refinery lines, batch cultivation, consolidated bioprocessing, enzymatic saccharification, etc., for co-production and extraction of industrially valued petrochemicals, prized pharmaceutically drugs, and other added-value compounds. The scopes of combinatorial-based approaches or techniques will also be regarded for future endeavors.