Display omitted •Magnesium oxyhydroxide colloid was obtained by pulsed laser ablation of Mg in water.•Magnesium oxyhydroxide lamellas effectively bind to the surface of the paper fibers.•Magnesium oxyhydroxide colloid treatment bleaches, hardens and stabilizes the paper.•The treatment proposed is highly effective and surpasses the conventional techniques. Magnesium-containing nanocolloids were synthesized by nanosecond pulsed laser ablation (PLAL) of a Mg target in water. As-prepared colloids contained 2-D lamellar nanostructures of magnesium oxyhydroxide Mg5O(OH)8 (Mg-NSs) with a thickness of 5–10 nm and a length/width up to one micron. The colloids obtained were used for the first time to restore old, low-quality paper (a Russian book from the beginning of the 20th century). All results were compared to conventional treatment with basic magnesium carbonate. It was found that Mg-NSs facilitated effective deacidification and conservation treatment of the paper. Paper pH increased after treatment and remained stable upon artificial aging. Moreover, treatment led to an increase in paper whiteness of up to 10% and paper strengthening up to 25%. In general, the treated paper became more resistant to the deterioration processes during aging. Thus, colloid of Mg5O(OH)8 lamellar nanostructures obtained by PLAL in water is a promising agent for paper restoration and conservation.