FTI replaces Maitland on the account.
The brief is global, with the exception of Australia, where Henderson will continue to use Cannings. However, the bulk of FTI's worth will be in the UK.
As well as financial calendar activity and corporate announcements, the brief is to work with Henderson to build its corporate presence and guide wider stakeholder engagement.
Henderson looks after assets worth £82bn. Headquartered in London, it is dual-listed on the London Stock Exchange and the Australian Securities Exchange. The firm is a member of the FTSE 250 and ASX 100, and has a market capitalisation of around £3.3bn.
Angela Warburton, global head of comms at Henderson, said: "As sector specialists, FTI Consulting’s financial services team know our industry and our issues extremely well. Our management team were attracted to their strategic thinking and senior counsel and we felt they were the right partners to accompany us on the next phase of our development."
Henderson has offices in 19 cities around the world and employs more than 900 people.
In January, former Henderson Global Investors head of comms Richard Acworth launched a new financial PR agency called Cornerstone with Ben Larter, formerly of JP Morgan Asset Management and BNY Mellon.