Bright will spearhead the agency's performance team and will be charged with helping to ensure the whole agency is focused on delivering business results for Initiative's range of clients.
He will work with brands such as Tesco, Sonos, Burger King, Match.com and Ancestry at Initiative.
Most recently, Bright worked at Mindshare as a business director developing the marketing of diverse brands such as American Express, Post Office, Anglian Home Improvements and News International.
Anna Watkins, managing director of Initiative UK, said: "Kristian is an incredibly high-calibre hire and I'm excited to have him on board at Initiative to continue to drive our investment in performance.
"Our performance team is key to us being able to help our clients achieve and measure their business results. After extensive research, I am confident Kristian is the best person to lead this team going forward."
Bright worked at MediaCom and PHD earlier in his career.
He said: "Initiative has an exciting and varied client base, which allows them to be at the forefront of performance-led planning. I'm delighted to take the opportunity to work with the fantastic team already in place to help realise this potential."
Bentall moved to Australia at the end of 2012.
Initiative's chief executive, Alex Altman, is to leave the agency as part of changes that will see Andy Jones, chief executive of sister agency UM London, take the role of chief executive of IPG Mediabrands UK and Ireland.Follow @MaisieMcCabe