The Justinian code consists of four books: (1) Codex Constitutionum, (2) Digesta, or Pandectae, (3) Institutiones, and (4) Novellae Constitutiones Post Codicem.

Work on the Codex Constitutionum began soon after Justinian's accession in 527, when he appointed a 10-man commission to go through all the known ordinances, or “constitutions,” issued by the emperors, weed out the contradictory and obsolescent material, and adapt all provisions to the circumstances of that time. The resultant 10-book Codex Constitutionum was promulgated in 529, all imperial ordinances not included in it being repealed. In 534 a new commission issued a revised Codex (Codex Repetitae Praelectionis) containing 12 books; the revisions were based partly on Justinian's own new legislation.

The Digesta (Pandects) was drawn up between 530 and 533 by a commission of 16 lawyers, under the presidency of the jurist Tribonian. They collected and examined all the known writings of all the authorized jurists; extracted from them whatever was deemed valuable, generally selecting only one extract on any given legal point; and rephrased the originals whenever necessary for clarity and conciseness. The results were published in 50 books, each book subdivided into titles. All juridical statements not selected for the Digesta were declared invalid and were thenceforth never to be cited at law.

The Institutiones, compiled and published in 533 under Tribonian's supervision and relying on such earlier texts as those of Gaius, was an elementary textbook, or outline, of legal institutions for the use of first-year law students.

The Novellae Constitutiones Post Codicem (or simply, in English, the Novels) comprised several collections of new ordinances issued by Justinian himself between 534 and 565, after publication of the revised Codex.

Latin was the language of all the works except the Novels, which were almost all published in Greek, though official Latin translations existed for the western Roman provinces.