The GSH Group, a national building repair and maintenance services firm, is planning to centralise all its UK-wide operational and administration activities in its headquarters in England.
It means the offices in Tarbert on Harris, where administration is carried out, are to close with the loss of 24 jobs. An office in Livingston is also under threat.
One local source said the GSH Tarbert office was given a 30-day notice of closure on Thursday.
The number and type of potential job losses is serious for Harris given the absence of alternative office-based, computing and administration employment on the island, which has a population of about 2,000. An added blow is that any redundancies would particularly hit a relatively young age group.
Isles SNP MSP Alasdair Allan said: "Harris is one of the most economically fragile communities in Scotland, and the loss of jobs would represent a severe blow."