This Upaniṣad, as its very name indicates, belongs to the Atharvaveda. It is also called Atharvaśīrṣa Upaniṣad. It is classified under minor Upaniṣads and consists of seven sections in prose.
The first section describes how the gods went to the svargaloka (heaven) and asked Rudra who he was. He replied that He was the primeval Supreme Person and that whatever existed was He. The gods then, realizing His supremacy, praised Him with their hands raised in adoration. The second and the third sections contain their hymns of praise. The fourth section defines and amplifies some of the epithets used in praising Rudra. The fifth section contains some well-known ṛks of the Ṛgveda and a description of the parts (a, u, m) of Om or Praṇava, including their symbology. The sixth section also contains some well-known mantras of the Ṛgveda and Kṛṣṇa Yajurveda. The last section is a eulogy of the results one gets by a study of this Upaniṣad.