Polyelectrolyte complexes (PECs) are self-assembled systems formed from oppositely charged polymers, used to create hydrogels for cell culture. This work was aimed at additive manufacturing 3D hydrogels made of a PEC between chitosan (Cs) and alginate, as well as their investigation for in vitro 3D ovarian cancer modeling. PEC hydrogels stability in cell culture medium demonstrated their suitability for long-term cell culture applications. Higher in vitro viability of two human ovarian cancer cell lines was detected at different time points on PEC hydrogels than on Cs hydrogels, used as a control. In addition, during the 63-day culture experiment, cells effectively colonized the scaffolds while retaining their aggressive tumor characteristics. A significantly lower sensitivity to cisplatin and eugenol, also when combined, was observed in the developed 3D ovarian cancer models, in comparison to what was achieved in relevant 2D cell cultures. The obtained results demonstrated therefore the suitability of the developed scaffolds for in vitro investigation of tumor modeling.