Bioabsorbable Zn–Mg alloys are considered an alternative to metallic fixators, but data on their biocompatibility at low Mg content remain insufficient. Aim — to evaluate the biocompatibility of Zn–Mg alloys containing 0.5–2 wt.% Mg in vitro and in vivo. Cytotoxicity of Zn–0.5Mg and Zn–1Mg powders (0.15–2.5 mg/mL) was assessed in direct contact with SCP‑1 cells (MTT assay). In vivo, cylindrical implants of four compositions were placed bilaterally into the tibial metaphysis of rabbits (n = 4). Complete blood count was performed on day 7; computed tomography (CT) was performed at 3 and 10 months. At 2.5 mg/mL, cell viability was 12.5 ± 1.0 % (Zn–0.5Mg) and 16.8 ± 1.6% (Zn–1Mg). At 1.25 mg/mL, Zn–1Mg showed no toxicity (101.4 ± 3.3 %), whereas Zn–0.5Mg remained cytotoxic (51.3 ± 4.4 %). Recovery to > 80 % viability was observed at 0.62 mg/mL for Zn–0.5Mg and 0.31 mg/mL for Zn–1Mg. In vivo, all animals maintained normal activity; haematological parameters were within normal range. At 3 months, CT showed stable implants without signs of osteolysis. Cortical bone density was 647.3 ± 5.4 HU, trabecular bone density was 510.5 ± 6.4 HU, comparable to intact bone. At 10 months, implants remained visible. Zn–Mg alloys with 0.5–2 wt.% Mg exhibit dose‑dependent cytotoxicity in vitro and satisfactory biocompatibility in vivo without systemic inflammatory reactions or bone resorption over 10 months. The alloy with 1% Mg has a more favourable cell viability profile.