The Gospel of John differs from the Synoptics in its style and manner of writing. In John’s Gospel we have the feeling that the exalted Lamb of God, the Messiah, the King, is speaking, while in the Synoptics the proclamation of the kingdom of God is at the center. The main theme of the Gospel is the faith of the John’s community which opposes Jewish unbelief. The Gospel of John speaks most of the importance of the Holy Spirit and is also called “spiritual.” The paper analyzes the role of the Holy Spirit in the Paschal Mystery based on three biblical texts: Jn 14: 15-31; Jn 16: 4-15; Jn 20: 19-23. In those texts, Jesus promises his disciples the Spirit, a mighty Defender at the Last Supper. For the "other" Defender to come, Jesus must leave. The Defender will encourage them and deepen the words of Christ. The disciples are confused, but Jesus is aware of the mission he received from the Father. During the arduous trial, after the humiliation, Jesus bravely steps towards his death on the Cross, i.e. towards his glorification on the Cross. On the one hand, Jesus’ death on the Cross means the sending of the Spirit to his followers, while on the other hand, it is proved that Jesus is the Passover lamb sacrificed for all mankind. Furthermore, the paper proves that the Holy Spirit is the third divine person, that he is a member of the Most Holy Trinity, and that he is God himself. Although he is often said to be an "unknown" God, he is very important in the Trinity. Since false teachings about the Spirit have appeared throughout history, the paper, based on the writings of Athanasius, Basil the Great and Gregory of Nazianzus, discusses the Spirit as God and thus as an equal member of the Trinity from John's perspective. The problem between the East and West arises with the addition of the Filioque to the Nicene-Constantinople Creed in the 6th century. This problem was tried to be resolved at various Councils, but it has remained unresolved to this day and is one of the causes of the schism between the East and West.