The forest cockchafer Melolontha hippocastani is one of the most dangerous forest pests in Central and Eastern Europe. The larval stage feeds on roots, causing serious damage to forest crops. Adult form feeds in tree crowns, resulting in their defoliation. This study is focused on assessing the morphological and genetic variability (mitochondrial COI gene polymorphism) of the cockchafer population under the natural feeding conditions of adult form. The beetles were collected from pine stands with admixture of birch from three forest districts located in eastern Poland. The studies have shown high homogeneity of morphological and genetic traits of the analysed population. In morphological features significant differences were found only in the length of the pygidium. This ultimately contributed to differences in the total length of the insect’s body. The COI gene analysis revealed the presence of 17 haplotypes. The average haplotype diversity (Hd) was 0.445, and the average nucleotide diversity (p) reached 0.00127. The values of Tajima’s D and Fu’s Fs tests were negative but not statistically significant. This suggested that there was no significant selective pressure on the studied populations, and the emergence of new haplo− types was a result of genetic drift. Each population had two gene pools, and their proportion was different in each of them. The low variation between the analysed populations could be the result of high gene flow and lack of complete geographic isolation. This was confirmed by the Fst index value of 0.0127, and the number of migrants per generation reaching 22 individuals. The high morphological and genetic uniformity observed in the studied populations indicates strong connectivity and the absence of significant environmental or geographical barriers limiting gene flow. This may reflect a high migratory potential of the species and its ability to rapidly colonize new areas. Combined with ongoing climate change and the expanding range of decid− uous tree species, these findings suggest a capacity for long−distance dispersal. For forest manage− ment practice, this highlights the need for protection measures not only at the local level but also on a broader landscape scale, taking into account the movement of beetles between forest com− plexes.