Tricia Quiller-Croasdell joined the Wales Office last week, having worked as deputy head of media operations at the UK's military headquarters for overseas operations.
Quiller-Croasdell also handled a stint in Afghanistan as the UK military media adviser based in Helmand.
The Wales Office's remit is to promote the best interests of Wales in the UK and is responsible for all areas not devolved to the Welsh Government.
Quiller-Croasdell will cover a broad portfolio including welfare, defence and energy.
She said: 'As the head of comms, I have been brought in to improve output, including better targeting of audiences and media organisations and increasing our engagement with key stakeholders.'
She oversees a team of four based between Whitehall and Cardiff Bay. Quiller-Croasdell replaces Andrew Mathias, who has returned to the Welsh Government to take up the post of head of comms and marketing to the Welsh Government's business minister Edwina Hart.
Quiller-Croasdell's replacement is still being recruited and because of current recruitment rules is likely to come from within the MoD.