The Goths first appear in historical record in the early 3rd century, and they were Christianized in the course of the 4th century. Information on the form of the Germanic paganism pracitced by the Goths before Christianization is thus limited to a comparably narrow and sparsely documented time-window in the 3rd and 4th centuries.
The center of the Gothic pagan cult was the village or clan (kuni), and the ritual sacrificial meal held by the villagers under the leadership of the reiks. The reiks saw themselves as the guardians of ethnic tradition. This was expressed starkly in the Gothic persecution of Christians in the 370s, when the reiks Athanaric saw this privilege threatened by the new religion, responding by the persecution of converted Goths (but not of Christian foreigners): according to the Passio of Sabas the Goth, Sabas was executed for professing Christianity (or rather for refusing to sacrifice to the tribal gods), while his companion, the priest Sansalas, was let go because he was a foreigner.
After the Goths had settled in Scythia in the 2nd century, it is probable that a process of ethnogenesis was set in motion, and that most of the "Goths" of the 3rd and 4th century were not in fact descended from Scandinavia but (much as was the case with the "Huns" in the following century) consisted of a heterogeneous population which was united under the name of "Goths" by virtue of having submitted to the elite formed by the ruling dynasties of the reiks.
Gothic paganism was thus a purely tribal religion, in which polytheism and ancestor worship were one and the same. We know that the Amali dynasty deified their ancestors, the Ansis (Aesir), and that the Tervingi opened battle with songs of praise for their ancestors.
The word god itself is derived from the Gothic word guth for a pagan idol (presumably a wooden statue of the kind paraded by Winguric on a chariot when he challenged the Gothic Christians to worship the tribal gods, executing them after they refused). It became the word for the Christian God in the Gothic Bible, changing its grammatical gender from neuter to masculine in this new sense only. The name of the Goths themselves is presumably related, meaning "those who libate" (while guth "idol" is the object of the act of libation). The words for "to sacrifice" and for "sacrificer" were blotan and blostreis, used in Biblical Gothic in the sense of "Christian worship" and "Christian priest".
One peculiarity which separates the Gothic pagan period from all other forms of Germanic paganism is the absence of weapons as grave goods. While pagan warrior graves in Scandinavia, England and Germany almost invariably contain weapons, and the practice is discontinued with Christianization, the pagan Goths do not seem to have felt the need to bury their dead with weapons (Wolfram p. 111: "Apparently [weapons] were of no use to the deceased Goths in the hereafter").
The gradual Christianisation of parts of the Gothic population came to a turning-point in the 370s. A civil strife between the Christian reiks Fritigern and the pagan reiks Athanaric prompted Roman military intervention on the side of the Christian party, leading to the Gothic War (376–382). In 376, the Romans allowed a number of ostensibly Christian Goths, including bishops and priests, to cross the Danube, but these "looked like clowns to the pagan Romans, and utterly scandalized the Roman Christians", supposing that they were in fact pagan Goths who had dressed up as Christian clerics in order to be granted asylum by the Romans.
A pagan Gothic belief in witches is attested with the story of the haliurun(n)ae (c.f. Anglo-Saxon hellrúne) who were expelled from the tribe by king Filimer, after which they mated with evil spirits and gave birth to the Huns, who eventually destroyed the Gothic empire. Wolfram compares the rejection of necromancy or witchcraft by the Goths with the pagan Scandinavian rejection of the seiðr of Finnic sorcerers or shamans.
Regarding the individual gods worshipped among the Goths, very little can be said with certainty. They did have a cult of a god of war, identified with Roman Mars, presumably a manifestation of Germanic Tiwaz, perhaps (on the basis on the letter names) called *Teiws in Gothic, among the Tervingi perhaps also known as "The Terwing", as the supposed eponymous ancestor of the tribe. Another important god may have been called *Fairguneis, identified with Roman Jupiter. Then, there was Gaut or Gapt, the ancestor of the Amali dynasty, and presumably eponymous of the entire people of the "Goths"; it is unclear whether this deity should be considered independent of those just mentioned, or if it is just another name by which either of them was also known; in any case, Old Norse Gaut in later centuries was considered a manifestation of Odin in Scandinavia. It may also be significant, that in the Eddaic tradition, Odin himself is said to have come to the north from the Russian region, i.e. the lands formerly inhabited by the Goths. If Gapt was the original "ansic" ancestor, later identified with Wodan-Odin, the Gothic letter name *ansuz (aza) may testify to his importance. Finally, the letter name enguz may testify to the existence of the god Ingwaz among the Goths, but there is no additional evidence for this. The river Danube may have also been deified, as *Donaws. In the light of comparative evidence from later forms of Germanic paganism, it seems possible that the "Germanic trinity" of Wodan-Tiwaz-Thonar may have had a parallel among the Goths, with Gapt, Teiws and Fairguneis; but this does not imply that Gapt should be assumed to have had the attributes typical of Viking Age Odin (Wolfram, p. 112: "The assumption of a Gothic Woden does not seem likely").