Abstract: A tissue-sampling brush is a medical device for acquiring internal patient tissue samples utilizing conventional endoscopic devices. The tissue-sampling brush features an elongated body that may be inserted into the channel of an endoscopic device and manually manipulated by a handle. The tissue-sampling brush is sleeved in a sheath during insertion into the patient's body with the plurality of bristles deploying from the sheath during sample acquisition. The sheath facilitates insertion and removal of the tissue-sampling brush into the endoscopic device as well as structural support and protection for the plurality of bristles and endoscopic device. A plurality of bristles is scraped against the interior walls of the patient's body in order to acquire a tissue sample. After acquisition, the plurality of bristles is retracted back into the sheath and any trickling sample is captured by a receptacle located adjacent to the plurality of bristles.