Protestant theology refers to the doctrines held by various Protestant traditions, which share some things in common but differ in others. In general, Protestant theology, as a subset of Christian theology, holds to faith in the Christian Bible, the Holy Trinity, salvation, sanctification, charity, evangelism, and the four last things.

Various Protestant denominations differ in their doctrine, with churches teaching either Wesleyan-Arminian theology, Reformed theology, or Baptist theology. Other evangelical bodies, such as the Lutheran Church–Missouri Synod, Presbyterian Church in America and the Evangelical Friends Church International may subscribe to what they see as the orthodox theology espoused by their historic tradition, such as Lutheranism, Presbyterianism or Quakerism respectively.

Mennonite Anabaptist beliefs were formulated in the Dordrecht Confession of Faith in 1632. Seven ordinances have been taught in many Conservative Mennonite churches, which include "baptism, communion, footwashing, marriage, anointing with oil, the holy kiss, and the prayer covering."

After becoming a believer, Anabaptist theology emphasizes "a faith that works." Anabaptist denominations teach:

... salvation by faith through grace, but such faith must bear “visible fruit in repentance, conversion, regeneration, obedience, and a new life dedicated to the love of God and the neighbor, by the power of the Holy Spirit.”

Obedience to Jesus and other New Testament teachings, loving one another and being at peace with others, and walking in holiness are seen as "earmarks of the saved." Good works thus have an important role in the life of an Anabaptist believer, with the teaching "that faith without works is a dead faith" (cf. James 2:26) occupying a cornerstone in Anabaptist Christianity. Anabaptists teach that in the believer, "justification begun a dynamic process by which the believer partook of the nature of Christ and was so enabled to live increasingly like Jesus." Christians of the Anabaptist tradition (who teach salvation by "faith that works") have argued that being a disciple of Jesus by careful obedience to New Testament commands (such as the holy kiss, baptism, communion, headcovering, and feet washing), is "crucial evidence that an individual has repented, believed, and yielded to Christ."

Baptists are those Christians who believe in credobaptism—that one should receive the ordinance of baptism after he/she experiences the New Birth. Baptists are categorized into two major categories: General Baptists (also known as Freewill Baptists) believe that Christ's atonement extends to all people, while the Particular Baptists (also known as Reformed Baptists) believe that it extends only to the elect. When the holiness movement came into being, some General Baptists accepted the teaching of a second work of grace and formed denominations that emphasized this belief, such as the Ohio Valley Association of the Christian Baptist Churches of God and the Holiness Baptist Association.

The doctrine of Baptist successionism (also known as Landmarkism), which has been influential among many Baptists, "argue[s] that their history can be traced across the centuries to New Testament times" and "claim[s] that Baptists have represented the true church" that "has been, present in every period of history". Baptists who uphold this ecclesiology also do not characterize themselves as being a Protestant Church due to their belief that "they did not descend from those churches that broke away in protest from the church of Rome. Rather, they had enjoyed a continuous historical existence from the time of the very first church in the New Testament days."