This paper tries to describe theoretically some of the numerous questions regarding the marriage in Justinian's time (525-565). By finishing the work of his predecessors (Gregorian, Hermogenian, Theodosius), Justinian codified the whole of Roman law. Of course, when we speak about Justinian, we also have in mind Tribonian and other members of his team. He introduced many innovations in family, i.e. marital relations: cognate kinship (blood kinship) replaced agnate kinship; the head of a family had no more „right of life or death“ (ius vitae ac necis) over the family members; marriage was reformed and a lot of restrictions were abolished as well as many pagan rituals involved in the act of getting married, and the divorce was no more „duty but right“. Under the influence of Christianity that was spread in the first century among slaves and the poor and the moral purity that had been preached by Christianity - Justinian continued the policy of his predecessors (August, Constantine, Theodosius) towards strengthening marriage and family. Even in the period of spreading Christianity across the Roman Empire, ancient Roman religious rituals were becoming less common due to decreased importance of religion and ethics. Roman legislation in that period did not insist on formalities in the process of getting married; it insisted on a mutual agreement of a bride and bride-groom and after that the marriage was contracted as a „legal union“ - consensus facit nuptias - as the Romans said. In the Justinian time, although the marriage was under a great influence of Christianity, it required no church blessing for a contracted marriage. That condition will be introduced by Leo the Wise in the 9th century for the Eastern Roman Empire. According to Justinian, a marriage is „the relationship of a husband and wife that contains permanent life community“. The procedure and the attached activities that accompany the act of getting married (engagement, dowry, premarital gift, prenuptial contract or instrimentum dotale, for the persons of higher classes) were contained in the provisions of Institution, Digest, Codex and Novellae and these have been referred to in the discussion about the topic in questions. Historical, comparative, legal and dogmatic methods have been used for the purpose of producing this paper. CONCLUSION: An analysis of provisions from the mentioned parts of Justinian's codification has lead us to a conclusion that they were the foundations for matrimonial legislation (with respect to both concluding marriage and divorce) in most states of the former Byzantine empire. Even today, only a secular marriage concluded before relevant state authorities is considered to be valid. Those wishing to be married in church are free to do so in the presence of the clergyman in charge, but this act has no legal effect. [ABSTRACT FROM AUTHOR]