The arch commemorates Titus' capture and sack of Jerusalem in 70, which effectively terminated the Jewish War which had begun in 66 (the Romans did not achieve complete victory until the fall of Masada in 73).

The Arch of Titus is in three bays with an ABA rhythm, articulated with a massive order of attached columns that stand on a high ashlar basement. The capitals are Corinthian, but with prominent volutes of the Ionic order scrolling out above the acanthus foliage, the earliest example of the Composite order. Above the main cornice rises a high weighty attic on which is a central tablet bearing the dedicatory inscription.

The entablatures break forward over the columns and in the wide central bay. Flanking the central arch, the side bays now each contain a shallow niche like a blind pedicular window, a discreet early 19th century restoration. The soffit of the archway is deeply coffered with a relief of the apotheosis of Titus at the center. The sculptural program also includes two panel reliefs that line the passageway. Both commemorate the joint triumph celebrated by Titus and his father Vespasian in the summer of 71.

One of the panels depicts the spoils taken from the Temple, while the other depicts Titus as triumphator attended by various genii and lictors. The soffit of the arch depicts the apotheosis of Titus.

The sculpture of the outer faces of the two great piers was lost when the Arch of Titus was incorporated in medieval defensive walling. The attic of the arch was originally crowned by more statuary, perhaps of a quadriga pulled by elephants.Based on the style of sculptural details, Domitian's favored architect Rabirius, sometimes credited with the Colosseum, may have executed the arch. Without contemporary documentation, however, attributions of Roman buildings on basis of style are considered shaky.

The arch is 21 m high, 25.7 m wide and 7.4 m deep. It has three archways, the central one being 11.5 m high and 6.5 m wide, the lateral archways 7.4 m by 3.4 m each. The lower part of the monument is built of marble blocks, the top (called attic) is brickwork reveted with marble. A staircase formed in the thickness of the arch is entered from a door at some height from the ground, in the end towards the Palatine Hill.

The general design with a main part structured by detached columns and an attic with the main inscription above is modelled after the example of the Arch of Septimius Severus on the Roman Forum. It has been suggested that the lower part of the arch is re-used from an older monument, probably from the times of the emperor Hadrian (Conforto et al., 2001; for a defence of the view that the whole arch was constructed in the 4th century.

The arch spans the Via Triumphalis, the way taken by the emperors when they entered the city in triumph. This route started at the Campus Martius, led through the Circus Maximus and around the Palatine Hill; immediately after the Arch of Constantine, the procession would turn left at the Meta Sudans and march along the Via Sacra to the Forum Romanum and on to the Capitoline Hill, passing both the Arches of Titus and Septimius Severus.

During the Middle Ages, the Arch of Constantine was incorporated into one of the family strongholds of ancient Rome. Works of restoration were first carried out in the 18th century; the last excavations have taken place in the late 1990s, just before the Great Jubilee of 2000.

The decoration of the arch heavily uses parts of older monuments, which are given a new meaning in the context of the Constantinian building. As it celebrates the victory of Constantine, the new "historic" friezes illustrating his campaign in Italy convey the central meaning: the praise of the emperor, both in battle and in his civilian duties. The other imagery supports this purpose: decoration taken from the "golden times" of the Empire under Trajan, Hadrian and Marcus Aurelius places Constantine next to these "good emperors", and the content of the pieces evokes images of the victorious and pious ruler.

Another explanation given for the re-use is the short time between the start of construction (late 312 at the earliest) and the dedication (summer 315), so the architects used existing artwork to make up for the lack of time to create new art. As yet another possible reason, it has often been suggested that the Romans of the 4th century lacked the artistic skill to produce acceptable artwork and therefore plundered the ancient buildings to adorn their contemporary monuments.