Taumarunui-born Elder, 34, captained the Chiefs in their first game, played against the Blues in May this year, a game the Chiefs won 39-12.
Announcing her signing, Elder said, "I'm looking forward to putting on the Chiefs jersey again. It was an honour to wear it earlier this year, and to get the opportunity to do that again is a real privilege.
"Growing up in the King Country, the Chiefs were my team, so supporting them all my life and now getting to wear their jersey, and play in those colours, is a really proud moment for me."
Elder was looking forward to reuniting with coach Allan Bunting, her coach in the Sevens programme.
"What's he's created in the sevens programme, and the legacy he's instilled in that jersey is pretty exciting for what he can offer to the Chiefs' jersey.
"I'm really lucky to be able to work alongside him and I know he'll bring some innovative ideas to the fifteens game," she said.
Bunting said he was delighted to have a player of Elder's ability in his squad.
"Les is a very well respected individual and rugby player for what she says, and has done on and off the field. She will be influential in what we are wanting to achieve. Les holds a lot of mana that will be invaluable for the development of this team," he said.
Before taking up her role, she will be with the Black Ferns squad on their end-of-year northern hemisphere tour with Tests against England and France.