Abstract Single-cell encapsulation using metal-phenolic networks (MPNs) is an emerging technique to protect cells from stressors. Until now, the MPN coatings have been only applied to some bacteria, yeast, and mammalian cells. To further demonstrate their versatility, we herein coat Chlamydomonas reinhardtii with the network consisting of tannic acid and iron(III). The encapsulation served as a mechanical barrier, which delayed proliferation of the coated cells. Furthermore, we investigated the adsorption of tannic acid onto the surface of C. reinhardtii and identified the optimum concentration to achieve partial coverage on the algae's surface. Finally, we explored the effect of MPN coating for flocculation-enhanced algae harvesting. Overall, the results demonstrate that the cell encapsulation technique using metal-phenolic networks is applicable to the C. reinhardtii, which is promising for the surface engineering of the green algae for energy harvesting and biomedical applications.