An anti-free flow device (16) is disclosed for a fluid administration system (10) having a tube assembly (12) engageable with a pump (14) with one end of the tube assembly (12) connected to a source of fluid (46) and the other end in fluid flow communication with a patient. The valve device (16) comprises a tube portion (18) defining a channel (22) in-line along a portion of the tube assembly (12) and a body (20) disposed and securely retained inside the channel. Fluid flow is allowed through the tube assembly (12) whenever the tube assembly (12) is in a stretched condition, such as when the tube assembly (12) is engaged with the pump (14). However, fluid free flow is prevented whenever the tube assembly (12) is in a relaxed condition or disengaged from the pump (14).