A prolific writer, his two main works, Pia desideria (1675) and Allgemeine Gottesgelehrtheit (1680), were published while he was the chief pastor in the Lutheran Church at Frankfurt.

[2] In Berlin, Spener was held in high honour, though the tendencies of the court and the government officials were rather rationalistic than pietistic.

Highly influenced by Johann Arndt, Lewis Bayly, Jean de Labadie, and Theophil Großgebauer, Spener's own writings display an emphasis on personal transformation through spiritual rebirth and renewal.

[6] In his Pia Desideria, he gave six proposals of how to enact this reform: (1) to more thoroughly acquaint believers with Scripture by means of private readings and study groups, in addition to preaching; (2) to increase the involvement of laity in all functions of the church; (3) to emphasize that believers put into practice their faith and knowledge of God; (4) to approach religious discussions with humility and love, avoiding controversy whenever possible; (5) to ensure that pastors are both well-educated and pious; and (6) to focus preaching on developing faith in ordinary believers.

[7] As these proposals indicate, Spener saw positive change for the church as being primarily dependent upon the pious involvement of individual believers.

The only two points on which he departed from the orthodox Lutheran faith of his day were the requirement of regeneration as the sine qua non of the true theologian, and the expectation of the conversion of the Jews and the fall of the Papacy as the prelude of the triumph of the Church.

[2] He did not, like the later Pietists, insist upon the necessity of a conscious crisis of conversion, nor did he encourage a complete breach between the Christian and the secular life.

[2] Spener was sometimes believed to be one of the godfathers of Count von Zinzendorf, the leader of the Moravian Brethren's Community at Herrnhut in Saxony.