The baptism performed by Jehovah's Witnesses organization, also known as the Watchtower Bible and Tract Society, is not valid because the religion is a non-Christian cult. It does not properly represent God, Jesus, and salvation. Instead, it teaches false doctrine in regard to the essentials of the Christian faith. Therefore, it's baptism is not true Christian baptism.
The Jehovah's Witnesses deny the doctrines of the Trinity, that Jesus is God in flesh, that he physically rose from the dead, and that salvation is by grace alone through faith alone in Christ. The Jehovah's Witness organization teaches that Jesus is Michael the Archangel who became flesh, that he did not physically rise from the dead, and that is necessary to keep the law and order to be saved.
The Watchtower organization baptizes in the name of the Father, the Son, and Holy Spirit. However, when getting baptized, the Jehovah's Witnesses must acknowledge that they are identifying themselves with Jehovah's spirit-directed organization. In other words, the baptism they undergo is according to the biblical formula, but in addition, is made to it with the identification with the Watchtower Bible and Tract Society as a true representative of God on earth.
Please consider the following references from Jehovah's Witness writings.
- There is no Trinity, (Let God be True, pp. 100-101; Make Sure of All Things, p. 386)
- "Jehovah's first creation was his 'only-begotten Son'. . . was used by Jehovah in creating all other things," (Aid to Bible Understanding, pp. 390-391)
- Jesus was Michael the archangel who became a man (The Watchtower, May 15, 1963, p. 307; The New World, 284).
- Jesus was raised "not a human creature, but a spirit" (Let God be True, p. 276).
- Good works are necessary for salvation (Studies in the Scriptures, Vol. 1, pp. 150, 152)
So, since the Jehovah's Witness organization denies essential doctrines of the Christian faith, it is not Christian and does not have proper authority to represent the true God in baptism. Its baptism is not valid and anyone who was baptized as a Jehovah's Witness must get rebaptized upon becoming a true Christian.
Matthew 28:19, "Go therefore and make disciples of all the nations, baptizing them in the name of the Father and the Son and the Holy Spirit."