Kiddushin is the last tractate in the order Nashim in the Mishnah, Tosefta, and both Talmuds. It deals with matrimonial matters. Its position at the end of the order is due to the fact that the order of the tractates is determined by their size and Kiddushin has only four chapters, less than all other tractates of Nashim. There is no corresponding word for kiddushin in English. It is more than an "engagement" in the current sense, as it can be dissolved only by divorce, and moreover the law of adultery, carrying the biblical death penalty, applies from the moment of kiddushin. On the other hand kiddushin is like "betrothal" in the sense that it represents a formal stage preliminary to marriage proper (nissu'in), the latter term referring to the induction of the wife into the husband's house, symbolized by the ḥuppah. Chapter 1, applying to kiddushin the term acquisition (kinyan), opens with the modes of kiddushin: by money, by writ, and by intercourse. The rest of the chapter deals with the acquisition of slaves and animals, of land and chattels, and with other extraneous matters. The chapter concludes with aggadic sayings. Chapter 2 deals mainly with kiddushin by proxy. Chapter 3 examines " kiddushin on condition" and "doubtful kiddushin," leading up to the problem of blemished descent. Chapter 4 deals mainly with questions of genealogy and bastardy. As usual, the tractate ends with homiletic material, on education, and after deliberating at length which craft to teach one's sons, reaches the conclusion that Torah study is the best vocation. In the Tosefta, this tractate is divided into five chapters.

Important masoretic observations are made in the Babylonian Talmud. It states that the scribes were called soferim because they counted (safar) the letters of the Torah; exact indications are then given as to the number of letters, words, and verses in the Pentateuch and in other parts of the Bible, and as to which letter, word, or verse mark the middle of the Pentateuch, the Psalms, or the Chronicles respectively (30a). Interesting is the characterization of various nations: Rome is credited with welfare, Persia with courage, Babylon is said to be poor and ignorant, and Arabia immoral. Elam is characterized by hypocrisy and arrogance (49b). Historically important is the account of the struggle between the Pharisees and John Hyrcanus (66a). According to the letter of R. Sherira Gaon, a considerable section of the beginning of the Gemara text (up to " Ve-ein davar aḥer kortah "; 3b) is of savoraic origin.

The first chapter of tractate Kiddushin belongs to an ancient collection of mishnayot. The manner in which the halakhic material is arranged in this chapter suggests that it might originally have been a separate tractate, on kinyanim, later perhaps prefixed to the tractate Kiddushin because it happened to start with the "acquisition" of the wife. In fact, in the Babylonian Talmud this chapter comprises half of the tractate. Its language is slightly archaic, and the conclusion of the first chapter: "whoever performs a single precept is well rewarded, his days are prolonged, and he inherits the land" similarly testifies to an early date. To the same category belong also the end of the third and the fourth chapter of the tractate, which contain early halakhot on forbidden marriages . The influence of Pumbedita is clearly perceptible in the editing of the Talmud of Kiddushin, even though it is possible to discern the large share of Ravina and R. Ashi in its final editing.