Photo-cross-linked ulvan scaffolds were designed with the aim to induce and support enzyme mediated formation of apatite minerals, in the absence of osteogenic growth factors. Scaffold formation with a desired geometry was investigated using chemically modified ulvan bearing radically polymerizable groups. Further bioactivity was incorporated by the use of alkaline phosphatase (ALP) induced minerals. Successful modification of UV cross-linked ulvan scaffolds was revealed by (1)H NMR. The presence of the mineral formation was evidenced by Raman spectroscopy and XRD techniques. Investigations of the morphology confirmed the homogeneous mineralization using ALP. The MC3T3 cell activity clearly showed that the mineralization of the biofunctionalized ulvan scaffolds was effective in improving the cellular activity.