The owners of the Western Mail, South Wales Echo, Wales on Sunday and the Celtic weekly newspapers, have announced job cuts in a restructuring.
The operation is to move to its new building by next summer
Between 10 and 17 jobs will be lost, which National Union of Journalists said made it "extremely concerned".
Media Wales says it plans a "multimedia 24/7 newsroom" combining all its operations for print and online.
Some managers will lose their jobs and redundancy volunteers will be sought in the sport and photographic departments.
In an message to staff, Media Wales editorial director and Western Mail editor Alan Edmunds said the company had to develop "a world-class multimedia editorial operation to meet the changing demands of our readers and customers".
Mr Edmunds said the company planned to integrate the Western Mail, South Wales Echo Wales on Sunday and Celtic series of weekly newspapers, plus all the magazines, into one operation.
He said he aimed to have the newsroom in place by the end of March in readiness for a move to the company's new HQ under construction next door to its current central Cardiff site by May or June.
He said the restructuring had the full support of senior management at Trinity Mirror, Media Wales's parent company.
"The proposed management structure will be leaner but will be extremely effective for the demands we face," he wrote.
Mr Edmunds said the company was seeking some redundancies in its photographic and sport departments, initially as volunteers.
"We anticipate the new structure operating with around 10 fewer people than we currently have, but the change will create some exciting new roles, particularly in multimedia."
Wales on Sunday editor Tim Gordon will take responsibility for online. Simon Farrington, former editor-in-chief of magazines and the Celtic titles, will become business development editor, but his old role will not be replaced.
However, the company will replace former South Wales Echo editor Richard Williams, who left recently.
A three-month consultation on the proposals is to begin immediately.
The NUJ said the company was seeking a reduction in the staffing level of 17 journalists across the titles but because of existing vacancies, that meant a reduction of 10 from the current level.
NUJ official Martin Shipton said: "These proposed job cuts - the third in five years - again reflect the demand for profit margins that are unsustainably high. We will oppose compulsory redundancies affecting our members.
"It is vital that the integrity and identity of our print titles are protected, that journalists retain control of editorial policy, and that quality is not sacrificed by placing a multiplicity of burdens on individual journalists."