A device for placing a seal around an implant in a blood vessel, and associated treatment kit are provided. This device (24) includes a hollow sheath (60) having a longitudinal axis (Y-Y′), and at least one release member (62), which may be deployed with respect to the sheath (60) between a retracted position in the sheath (60) and an extracted position out of the sheath (60). The device (24) includes, for said or each release member (62), a seal body (64) having an angular extent strictly less than 360° around the longitudinal axis (Y-Y′), the seal body (64) being releasably attached onto the release member (62) so as to be released from the release member (62).
