Neo-Evangelicalism is the trend that started in the Fundamentalist movement in the middle of the twentieth century, among conservative Protestants, as a rejection of Fundamentalist separatism. Fundamentalism had arisen in reaction to liberal accommodation of the principles of the Enlightenment (in theology, called Modernism; in ethics, referred to as The social gospel). In the 1920s and 1930s, the conflict between the Fundamentalists and Modernists came to a crisis in many Protestant denominations, especially in the United States and Canada. Some Fundamentalists strongly advocated separation from the denominations and institutions in which Modernism had gained control, but others strongly urged that separation was not the appropriate response. These latter fundamentalist leaders called themselves "neo-evangelicals".

The term "Evangelical" was originally the self-description of both, the Modernists and the Fundamentalists. The word comes from the Greek word for "Gospel" or "good news": evangelion. "Evangelical" was the historic name of self-identification preferred by the first Reformed and Lutheran churches, and later indiscriminately referred to any Protestant tradition conforming to the ecumenical creeds (Athanasian, Nicene, Chalcedon) which placed prominent emphasis on the preaching of the Gospel.

By contrast, "neo-evangelicalism" described the fundamentalist contention that the evangel, the Gospel, is not found everywhere in the Evangelical churches. The Evangelicalism of the 19th century had not survived intact, they said, and on the one hand its Modernist heirs had surrendered their heritage as Evangelicals by accommodating the views and values of the world, and on the other hand Fundamentalists had over-reacted in their rejection of the Social gospel. The Modernists lost their identity as Evangelicals, and the Fundamentalists had lost the character of Evangelicalism, the writers argued. The Gospel must be re-asserted, restated in a new way, over against the alternatives: thus the term, "Neo-" (new or renewed) "evangelicalism".

The neo-evangelicals rejected the separatism of the "come-outer" fundamentalists. Separatist fundamentalism was not the world-changing faith of the previous two centuries, but was rather bitterly defensive, fear-bound, and irrelevant, they said. The call went out to reject these attitudes, and to engage the modern world in a positive way: to separate from worldliness but not from the world, to confront the world and worldly Christians on the world's own ground, not to shout them down, but to reach out to them with articulate and compassionate answers to the issues that most press upon the world. In the context of the increasingly bitter Fundamentalist-Modernist controversy this approach was new, and had tremendous popular appeal. It also drew a vigorous negative reaction from fellow Fundamentalists, who increasingly believed that their cause was being betrayed from within.

Chief figures at the outset of this attempt to transform Fundamentalism were the scholars Edward Carnell, Bernard Ramm, and Harold Ockenga who with Carl F. H. Henry edited the neo-evangelical magazine Christianity Today. Fuller Seminary (California) also aligned itself with the new perspective, and began producing graduates with non-traditional attitudes and methods. Also, Wheaton College (Illinois) shaped an undergraduate curriculum that promoted the new ideals of vigorous and open engagement with the culture, and from that program came its most famous and influential graduate: the mass-crusade evangelist Billy Graham. The scope of this movement was so broad, and its influence so pervasive, that the New of its self-applied name soon seemed redundant to observers, so that it became known to the world as simply Evangelicalism. The term, neo-evangelicalism, is still self-descriptive but only when referring to its beginnings in the 1940s and 1950s. It is now used almost exclusively by critics, to distinguish themselves from this movement.

The most obvious feature of this new Evangelicalism is the rejection of denomination-centric concerns. Its base of operation is not in the churches, but in a vast, decentralized array of organizations created to bridge the gap between the churches and the culture. This approach is called the parachurch model, which literally means "beyond church". This model had been pioneered in the Second Great Awakening of the 19th century, but it was perfected in the second half of the 20th century.

The parachurches are businesses, non-profit corporations, and private associations that serve no particular church or association of churches, while attempting to avoid encroachment into roles traditionally reserved for the churches alone. Numerous crusade-evangelist associations patterned after Billy Graham's broad ecumenical model are only one type of example. Contemporary music and print publishers, radio and television stations, film studios, study centers and institutes, grade schools and colleges were started without sponsorship of any particular denomination, and ideally promoted no particular tradition within the broad spectrum of Evangelicalism. Mass events such as the Promise Keepers, campus organizations such as Campus Crusade for Christ, InterVarsity Christian Fellowship, Youth for Christ, Youth with a Mission, and Navigators, a plethora of political, social activist, and self-help and Bible study organizations, all have in common this parachurch model. A deliberate neutrality toward denominational issues is cultivated. However, most parachurch organizations adopt a "Statement of Faith" or creed with which they require members to agree. Some statements try to remain as vague as possible while remaining Christian, while others are more specific and can be identified with a particular family of protestant denominations. These statements of faith do not impose doctrinal standards, but rather serve as one symbolic element in the gestalt identity which evangelicals believe they share but find difficult to describe.

From the beginning, the popularized movement expressed a distinction between its message, and what some Evangelicals might call "religion", or "churchianity". Evangelicalism today is broader than ever, and its reach beyond all traditional conceptions of the church is more obvious.

While it continues to thrive within the denominational churches, the movement has burst these bounds. It moves in antithesis to "traditionalism", "dead orthodoxy", and "irrelevance". Some influential Evangelical Churches have been created on the model of parachurch organizations. As in the parachurches, doctrinal formulations, which may exclude congregants of diverse backgrounds, are often avoided. These are unaffiliated churches, or churches that bury all reference to their affiliation, custom-created to serve particular target populations. The most progressive of these Evangelical churches defy categorization: holding multi-media productions, concerts and drama presentations, rather than religious services as traditionally understood. The same churches may also hold alternative services especially designed to appeal to those with more traditional tastes. Evangelical house church projects have been established in some neighborhoods, which may even avoid using the word "church" to describe their meetings. Special meeting places, a professional clergy, even the sacraments might be set aside by an Evangelical church, in some cases: not necessarily on account of convictions that these institutions are wrong, but rather in order to extend outreach beyond traditional bounds. One of the first denominations to discontinue the practice of Baptism and Communion for these reasons was the Salvation Army, founded in the late nineteenth century.

Criticisms of the movement are as diverse as the movement itself. It has certainly explored a wide swathe of the territory opened to it by the rejection of the Fundamentalist principle of separation, and no doubt, it will go farther in the future. In the process, it has provoked the anger and alarm of many. But, without controversy, the Neo-evangelical movement has been the most influential development in Protestant Christianity in the second half of the 20th century.