- Predestination - Boettner is best known for his defense of Calvinist soteriology, particularly the doctrine of predestination. He argued that God, in His sovereignty, has foreordained all events, including the salvation of individuals, based entirely on His grace and not on human merit. This view was comprehensively outlined in The Reformed Doctrine of Predestination.
- Scriptural Authority - Boettner upheld the inerrancy and authority of Scripture as the foundation of all Christian theology. He emphasized that theological doctrines must align with the clear teaching of the Bible, a view evident in his works like The Inspiration of the Scriptures.
- Salvation by Grace Alone - Consistent with Reformed theology, Boettner emphasized salvation by grace through faith. He rejected any notion of human works contributing to salvation, insisting that it is solely the work of God's sovereign grace.
- The Role of the Church - Boettner viewed the Church as the visible manifestation of God's Kingdom on earth. He believed the Church had a vital role in evangelism, education, and the moral transformation of society.
- Postmillennialism - Boettner was a staunch advocate of postmillennialism, the belief that the Kingdom of God is currently expanding through the preaching of the Gospel and the work of the Holy Spirit. He held that this growth would lead to a long era of peace and righteousness before the second coming of Christ. His book The Millennium articulates this optimistic eschatological perspective.
- The Eternal State - In discussing life after death, Boettner upheld the biblical teaching on the eternal state of the saved and the lost. He maintained that believers would enjoy eternal life in the presence of God, while unbelievers would face eternal separation and judgment.
Trinitarian Theology - Boettner articulated a classical understanding of the Trinity, affirming the co-equality and co-eternality of the Father, Son, and Holy Spirit. He presented this doctrine as essential to orthodox Christian belief, as detailed in his work The Trinity.