The basilica is part of a complex composed of:

A 6th-century octagonal baptistry. Built in the 5th century together with the pre-Euphrasian basilica, and underwent considerable alterations. A 16th-century bell tower. A colonnaded atrium. Built after the basilica, it is covered on all four sides by a portico which houses a rich collection of stone monuments. An Episcopal residence (The Bishop's Palace), also built in the 6th century. Very little remains of the original building. A trefoil-shaped memorial chapel, built in the 17th and 19th centuries.

Basilica entrance. The two aisles are separated from the nave by 18 elegant Greek marble colonnades with richly sculpted Byzantine and Romanesque capitals, decorated with depictions of animals. They all carry the monogram of Saint Euphrasius. The arches between the capitals are decorated with stucco work.

A novelty of the Euphrasian basilica is that rather than being enclosed by a straight wall, as all sacred buildings were up to that time, it makes use of the breadth and length of the apse of the central nave, built in the shape of a polygon from the outside, whilst the two aisles end in smaller semicircular apses, hollowed into the wall. Thus the Euphrasian basilica is the earliest example of a triple-apsed church in Western Europe. The atrium is a typical example of Byzantine architecture, as are the columns, the tiles on the altar rail and all the abundant mosaics. Most impressive is the representation of Christ with the apostles, and beneath it a frieze of 13 medallions with a picture of Christ as the Lamb in the centre, surrounded by 12 medallions depicting various martyrs