The mandate follows the launch of its new Oslo-based office, its second in the Nordic region, where it will offer onshore depositary services to buy-side firms.
The Nordics has become a key region for custodians to expand their capabilities, as many have established new on-the-ground presence.
Regulatory and operational costs factors may require regional CSDs to band together and overcome these new pressures.
The mandate will include global custody and fund administration services for Storebrand's AIF and UCITS Luxembourg-domiciled funds.
Citi already offers direct custody and clearing services in Denmark, Finland and Sweden, with expansion taking its European sub-custody network to 37 markets.
The deal comes six months after Torstone entered the Norwegian market following its connection to the local CSD.