The office was established in Athens by the lawyer George Koutsonassios in the year 1954. The office from the year 1954 to the year 1982, managed by George Koutsonassios, had as a line of activities mainly cases of Civil Law and its clients were companies resident in Athens and private persons. During those years the office was specialized in cases of Law of Property, Law of Succession and Law of Insurance.
Since 1982 the lawyer Christos Koutsonassios, George Koutsonassios son, concerned actively himself with the office' s cases and extended the line of activities in cases of International Trade Law as well as in cases of Competition Law, Law of Literary and Industrial property.

In the year 1994 the lawyer Christos Koutsonassios takes over the management of the office and the clientele is expanding in foreign companies as well as foreign private persons, largely from the german - speaking European countries (Germany, Austria, and Switzerland). The office participates as a member in international unions of law offices.

The professional experience, the credibility the scientific method and the consistency and trust in the client were the beliefs that the founder of the office, George Koutsonassios taught and which the partners of the office keep following today.