This research examines the testimony of witnesses and their respective applications under the Islamic law and contemporary laws, as the most common means of proof among the disputants. The purpose of the study is to prove the opponent's claim or defense. The research deals with the definition of the testimony, its significance, its legitimacy as a piece of evidence, and the requirements involved for its admissibility. The findings of this paper include the permissibility of the testimony of women alone, in cases such as breastfeeding and initiation of the child for inheritance, as well as the defect in a woman’s testimony and that a woman is forbidden from changing her testimony before the final judgment is passed. In addition, this research has found that testimony of a mute person is considered to be invalid according to the present Omani law, an issue needs to be addressed by the country’s legislators.