The invention concerns a medical sensor assembly comprising a flexible plaster (10) adapted for adhesion on the skin (12) of a patient and a sensor (14) configured for transdermal measuring a physiological parameter, wherein the sensor (14) has a measuring part (36) insertable into the skin (12) and a contact part (38) for providing a signal connection to a measuring unit. It is proposed that the plaster (10) has a flap (16) which is adhered to an intermediate section (40) of the sensor (14) between the measuring part (36) and the contact part (38).