The agency joined forces with its sister agency Tequila and the media agency OMD International, seeing off competition from Leo Burnett and DraftFCB London.
The scope of work includes a £2.5 million advertising campaign that will run across the UK, Europe and Russian markets later this year.
It will focus on positioning Capital Partners as an up-market property company that champions environmental responsibility in the areas in which it operates.
The work, currently in the early stages of creative development, will target environmentally conscious, high-spending Europeans, who are looking to invest in foreign property.
The brief will see TBWA\London and Tequila work alongside the brand consultancy agency Interbrand, the public relations company Weber Shandwick and the destination consulting group Locum.
Steve Henry, the executive creative director of TBWA\London, said: "From the outset, we were really impressed with the uncompromising passion of Capital Partners and its commitment to doing things differently."
Specific media for the campaign has not yet been confirmed, but it is believed to include print ads, television and digital executions.