Induced resistance in plants is a promising strategy for pest management, helping to reduce dependence on synthetic pesticides. However, no study has yet examined the interaction between Tetranychus urticae and Aronia melanocarpa, including host acceptance, performance, and antioxidant defence mechanisms. In this study, host acceptance of T. urticae was evaluated using two A. melanocarpa ecotypes: a non-cultivar (AMe) and the cultivated variety ‘Galicjanka’ (AGe). Leaf morphological traits (trichome density and length) and key life-history parameters of the mite (fecundity, egg development time, and larval duration) were assessed. Mite feeding effects on oxidative stress markers (hydrogen peroxide—H2O2; thiobarbituric acid reactive substances—TBARS) and antioxidant enzyme activity (guaiacol peroxidase—GPX ascorbate peroxidase—APX) were analysed by ecotype and infestation duration. Results showed low fecundity and prolonged development, indi- cating that neither ecotype is a preferred host for T. urticae. Ecotype-dependent differences in acceptance and mite performance suggest that variation in trichome density and bio- chemical traits may influence susceptibility. Baseline differences in H2O2 and TBARS imply a role in constitutive resistance, while their induction, accompanied by increased GPX and APX activity, highlights oxidative stress and antioxidant defences as key components of A. melanocarpa responses to mite attack.