Yeldham, who joins next month, will lead an 11-strong team formed from a review of comms carried out by Grant Riches Communications last summer.
He joins from the Greater London Authority, where as head of office he advises Labour Party assembly members on communication and policy issues.
At Lewisham, a priority for Yeldham will be to drive through a newly created strategy to make marketing and communications more 'campaign focused'.
Grant Riches associate Dee Sullivan, who has been covering Yeldham's role on a part-time basis since last year, said: 'What we want to do is have this campaign approach running through all the work we do, to have marcomms followed by internal communications with media relations work supporting that.
'One of the main areas is a campaign on recycling. I hate the phrase "joined-up approach" but that does best describe what we are trying to do,' she added.
Lewisham PRO Rebecca Hosgood added that the make-up of the new team, which includes design and photography officers and one, instead of two, media relations managers reflected this approach.
The team also includes Institution of Highways and Transportation head of marketing Michelle Fahey as marketing communications manager, and Philippa Berrington-Davies, who joins from the London Borough of Newham as media relations manager. Both also join next month.
Prior to joining the GLA, Yeldham was a Labour Party press officer, where his work included campaigning for Frank Dobson's unsuccessful London mayoral bid.
He is also a member of the Chartered Institute of Public Relations' local government committee.