A sideport connector for an IV catheterization system is disclosed in which a secure connection can be maintained with standard Y-shaped sideport connectors, such as a septum-type connector. The connector of the present invention comprises a clip having a collar which slidably and, optionally, rotatably engages the septum in order to prevent accidental disengagement. The clip is prevented from disengaging motion by, preferably, a ratchet-pawl mechanism. In another embodiment, the clip can be mounted on the branch of the Y-shaped sideport. The connector also comprises a needle shield or, optionally, a cap to prevent self-injection and contamination.