This paper discusses a unique rock inscription found during the 2011 survey conducted by the author in the area of Ja'alan Bani Bu Hasan in the Southern Sharqiyah Province, Oman. This type of inscriptions is not recorded in the northern part of Oman, and is frequently found in the south. Since the beginning of the twentieth century, several amateurs and travelers have reported the discovery of many of these inscriptions in the Province of Dhofar. Several of these inscriptions have been found near tombs and triliths in Dhofar. This is also the case with the Ja'alan's rock inscription which was found near one of the triliths recorded in the area of Saih al-Sa'ad. This type of inscription was not previously found by any traveler or researcher working in the northern and central parts of Oman. For example, in 1970s, the British expedition carried out an archaeological survey in the eastern region of Oman and documented a number of archaeological features, including a large number of prehistoric tombs and triliths, but did not find such an inscription. Hence, the discovery of Ja'alan rock inscription with its letters or symbols is the first of its kind in the eastern region of Oman. Although they have been frequently found, their symbols or characters have not yet been fully decoded. Therefore, the available information does not help understanding several related aspects including their content, meaning, purpose, as well as their dating, and who executed them; all of which remain unanswered. This paper attempts to present the Ja'alan inscription, and compare it with similar inscriptions from other areas, particularly Dhofar. This will be done in order to understand its content and dating, as well as the distribution of this type of inscriptions in Oman.