An isolation procedure for proteins from duckweed was optimized based on a previously developed method for protein isolation from sugar beet leaves. Optimization included the protocol for disrupting cells and protein recovery. With the optimized protocol, protein was isolated (protein yield 14.2%, RuBisCO yield 27%). The concentrate was off-white and contained 67.2% protein. The isolation procedure resulted in a large enrichment in RuBisCO (from 48% to 92%). Denaturation of duckweed protein concentrate was observed at 62 °C at pH 7, while heating at pH 4 did not show denaturation peaks. Solubility was good far from the iso-electric point and showed a minimum around pH 5. Gelling was better at pH 7 than at pH 4. At pH 7, duckweed gels were much stronger than soy and only slightly weaker compared to egg white protein, while at pH 4 duckweed gel strength was similar to soy and lower than egg white.