Purpose: This study aims to employ five marine Pseudoalteromonas strains, belonging to Psa. arctica DSM 18437T, Psa. carrageenovora DSM 6820T, Psa. issachenkonii LMG 19697T, Psa. rubra DSM 6842T and Psa. tunicata DSM 14096T to ferment brown crab processing side streams. Methods: The generated hydrolysates after the fermentation were screened for their antioxidant, anthelmintic and anti-biofilm activities. Results: After 72 h, the highest degree of hydrolysis (DoH) of 14.92% was reached by Psa. issachenkonii. The highest 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging ability was obtained by hydrolysates of Psa. rubra with an IC50 of 2.23 mg/mL while for the 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging ability, the maximum was reached by the hydrolysates of Psa. tunicata with an IC50 of 1.23 mg/mL. Anthelmintic activity, as tested on Caenorhabditis elegans, revealed a 99% mortality rate at 1 mg/mL with ethyl acetate extracts of the hydrolysates of Psa. arctica, Psa. issachenkonii and Psa. rubra. In terms of antibiofilm activity, aqueous extracts of the hydrolysates of Psa. arctica and Psa. issachenkonii at 500 µg/mL could dramatically decrease the biofilm formation index of Staphylococcus epidermidis RP62A from 1.35 to 0.37 and 0.36, respectively. Conclusions: Brown crab processing side streams could be valorized by marine Pseudoalteromonas bacteria fermentation for the production of a mixture of bioactive compounds. Graphic Abstract: [Figure not available: see fulltext.].