It is aimed at teachers who have dropped out of the profession because of family commitments who might like to return part-time or those who would like to scale-down their commitment.
NUT Cymru hopes the register will be used by teachers, schools and local education authorities. Many teachers are not aware of their legal right to share jobs, it says, and others would like to share jobs but do not know how to find a partner teacher.
Opposition to job-sharing is still to be found in some local authorities but the chief difficulty lies in getting school governors to accept it, says Heledd Hayes, the union's education officer.
The union believes that job-sharing would appeal to parents with young children, people looking after elderly relatives or wanting to work part-time for health or study reasons.
Only a few men have so far applied to join the register but the NUT hopes more will. "After all, they have responsibilities these days as well - and we believe in equal opportunities," says Heledd Hayes.
NUT Cymru can be contacted on 01222 491818.