The present invention relates to an insert for an optical fiber assembly reliably retaining an optical cable by preventing an axial and rotational movement thereof and further to an optical fiber assembly using such an insert. The insert is provided for guiding a part of the optical cable (12) which comprises at least one optical fiber element (14) and being accommodated in a housing of the optical fiber assembly, wherein said part of the optical cable (12) has a cut-out portion (16) in which a jacket (10) of said optical cable (12) is partially removed, thereby exposing said at least one optical fiber element (14). The insert (2) comprises an optical cable guidance means (8) for guiding said optical cable (12) across the insert (2); a recess (26) surrounding the exposed optical fiber element (12) and form fit means (32, 34) for suppressing an axial and rotational movement of the optical cable (12), wherein said form fit means (32, 34) are adapted to abut against surfaces of said jacket in the cut-out portion (16).