Separately, it has won a project on the WKD drinks account; it has been briefed to create the alcoholic drink brand's summer campaign.
Nitro pitched with its recently acquired direct marketing operation, River Communications, to win the two accounts. Activity on both will be above and below the line.
The Credit Suisse win sees Nitro take on the company's Winterthur Life pensions and investment brand. Nitro's campaign will be its first national consumer work as it looks to raise its profile and highlight its offerings.
A press and outdoor campaign will use the line: "Pensions in black and white." It will feature prominently around rugby matches in which the New Zealand All Blacks are playing. Initiative has been appointed to handle the media buying.
In the WKD pitch, Nitro beat the incumbent, Big Communications, and Golley Slater. Big will continue to do some work on the brand, with Nitro handling the bulk of the account.
Previous work on WKD has included TV ads showing men playing tricks on each other, using the line: "Find your WKD side."