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Τhis work describes the synthesis of PLA-grafted M-alginate (g-M-alginate; M: Ca²⁺, Co²⁺, Ni²⁺, Cu²⁺) aerogels. <i>DL</i>-lactide (LA) was attached on the surface of preformed M-alginate beads and was polymerized, using stannous octoate as catalyst and the –OH groups of the alginate backbone as initiators/points of attachment. The material properties of g-M-alginate aerogels were not affected much by grafting, because the linear PLA chains grew on the M-alginate framework like a brush and did not bridge their points of attachment as in polyurea-crosslinked M-alginate aerogels. Thus, all g-M-alginate aerogels retained the fibrous morphology of their parent M-alginate aerogels, and they were lightweight (bulk densities up to 0.24 g cm⁻³), macroporous/mesoporous materials with high porosities (up to 96% <i>v</i>/<i>v</i>). The BET surface areas were in the range of 154–542 m² g⁻¹, depending on the metal, the nature of the alginate framework and the PLA content. The latter was found at about 15% <i>w</i>/<i>w</i> for Ca- and Ni-based materials and at about 29% <i>w</i>/<i>w</i> for Co- and Cu-based materials. Overall, we have demonstrated a new methodology for the functionalization of alginate aerogels that opens the way to the synthesis of polylactide-crosslinked alginate aerogels with the use of multifunctional monomers.