His first work covered the history of the Church, from the Ascension of Jesus to the defeat of Licinius in 323, in twelve books. His sources for it included Eusebius of Caesarea, the Clementine homilies, Hegesippus, and Sextus Julius Africanus.
Sozomen's second work continues approximately where his first work left off. He wrote it in Constantinople, around the years 440 to 443 and dedicated it to Emperor Theodosius II.
The work is structured into nine books, roughly arranged along the reigns of Roman Emperors:
Book I: from the conversion of Constantine I until the Council of Nicea (312–325)
Book II: from the Council of Nicea to Constantine's death (325–337)
Book III: from the death of Constantine I to the death of Constans I (337–350)
Book IV: from the death of Constans I to the death of Constantius II (350–361)
Book V: from the death of Constantius II to the death of Julian the Apostate (361–363)
Book VI: from the death of Julian to the death of Valens (363–375)
Book VII: from the death of Valens to the death of Theodosius I (375–395)
Book VIII: from the death of Theodosius I to the death of Arcadius (395–408).
Book IX: from the death of Arcadius to the accession of Valentinian III (408–25).