Hydrogel has been used as an alternative to replace biocide-based paint in preventing biofouling. However, hydrogel has low adhesion on metallic substrate, hindering its application for coating. Therefore, the aim of this project is to enhance the adhesion strength and anti-biofouling properties of the poly(acrylamide-co-acrylic acid)/polyethylene-glycol hydrogel, poly(AAm-co-AAc/EG) coating via the incorporation of fly ash-based geopolymer that range from 0.5 wt to 2.5 wt. The hydrogel coating was synthesised via free radical polymerisation with the aid of N,N-methylenebisacrylamide (MBA) as the crosslinker, and ammonium persulfate (APS) as the initiator. The Fourier transform infrared (FTIR) spectra of the hybrid hydrogel had proved the presence of geopolymer with the availability of significant peaks at 3,294 cm-1 (N-H bond), 2,946 cm-1 (O-H bond), 1,545 cm-1 (C-O-C bond) and 1,113 cm-1 (Si-O-Si or Al-O-Si bond). The average swelling capacity of the hybrid hydrogel coating in distilled water (up to 50,000 ) was significantly higher than in artificial seawater (up to 5,000 ) due to osmotic pressure difference. The anti-biofouling performance test by using algae (Chlorella vulgaris sp.) suspension showed that the incorporation of 2.0 wt geopolymer into hybrid hydrogel coating had successfully reduced the algae attachment on the substrate by 92 as compared to the control sample. The adhesion strength of all hydrogel coatings was investigated by using the pull-off adhesion test in accordance to ASTM D4541. The incorporation of 2.0 wt geopolymer into hydrogel matrices demonstrated an increment of 58 in adhesion strength on steel plate as compared to neat hydrogel. The results showed that geopolymer has the potential to improve the anti-biofouling and adhesion strength of hydrogel coating. © 2020 AIDIC Servizi S.r.l.