A foldable brush self-sampling device for collecting of cell specimens from a body cavity, such as cervix, endometrium, rectum, nasal cavity and fauces, for diagnostic purposes, allows a user to collect cell specimens in the privacy of home. The device includes a sheath and a brush bar. The brush bar would fold into the sheath, which is with smaller diameter. The user inserts the sheath into the cavity easily and pushes the brush bar to expose the brush elements. After insertion of the sheath and push of the brush bar, the brush bar is rotated to obtain the specimen from the body cavity and then retracted in order to return the sheath.