The ability to adapt to changing environmental conditions is critical for any species to survive. Many environmental changes occur too rapidly for an organism’s genome to adapt in time. Accordingly, being able to modify either its own phenotype or the phenotype of its offspring to better suit future anticipated environmental conditions could afford an organism a significant advantage. However, a range of animal models and human epidemiological data sets are now showing that environmental factors such as changes in the quality or quantity of an individual’s diet, temperature, stress or exposure to pollutants can all adversely affect the quality of parental gametes, the development of the preimplantation embryo and the health and well-being of offspring over multiple generations. This chapter will examine transgenerational effects of both maternal and paternal environmental factors on offspring development and well-being in both human and animal model studies. Changes in the epigenetic status of either parental or grandparental gametes provide one candidate mechanism through which the impacts of environmental experience can be passed from one generation to another. This chapter will therefore also focus on the impact of parental and grandparental factors on epigenetic transgenerational inheritance and offspring phenotype.