The vocation to parenthood is one of the basic tasks of the spouses. In the modern world marital infertility is one of the ever more common problems affecting married couples. On the other hand, ever more often we encounter situations, in which parents, especially single mothers, do not want to raise their children. The meeting of the needs of people in both these situations makes the so-called unwanted or rejected children get a chance to find parental love and a family home by means of adoption. The article tackles the issue of adoption present in the teaching of the Magisterium of the Church. It indicates that accepting a born child to the family through adoption is a requirement of the spouses' fertile love, but also a Christian fulfillment of the commandment of love, the service to life and a way to preach the 'Gospel of life' by means of acts of love given to the most needy child. Adoption is not an easy thing, an event that happens once, but it amounts to saying 'yes' to love; it is accepting a certain way of life, in which serving another man and Christ present in the 'least' man is the first and supreme aim of adoptive parents' life. It is also worth stressing that the necessity to shape and create mentality serves a man not as something exceptional, but exactly as the style of life of Christian spouses.