• The beech marten gives birth to three or four young, which are blind and naked at first. Eight months pass between mating and birth, and the gestation period lasts only one month.
• The beech marten's mating occurs during the summer months from June to August, but due to the conservation of sperm in the female's body, the offspring are born in spring, from March to April.

Embryonic development is 4 weeks. Litter size is 2–6. Maturity occurs from 1 to 2 years. Offspring are 2–6. Mating occurs in summer. Due to delayed development, young are born in spring. The mother cares for them alone. The reproductive interval is 1 year. They inhabit and develop on land, outside of water bodies. Eggs, or young develop in a nest built on the ground or close to it. The nest is hidden in an underground burrow. A caring mother—the nest is hidden in an underground burrow, only the mother shows parental care for the offspring. In tree cavities and caves—the nest is inside the trunk of a tree or in a cave/crevice, both parents show some care. A caring father—the nest is inside the trunk of a tree or in a cave/crevice, only the father shows parental care for the offspring. Live birth—young are born live on land, they do not hatch from eggs or larvae. Ordinary sexual—homogamy, reproduction always with fertilization, without alternation of generations.