The C$500m ($478m) Canada Investment Fund for Africa has bought a portion of the 5 per cent stake that Poulina offered to international investors in its flotation on 19 August.
The fund, which is managed by UK private equity group Actis and the US group Cordiant, did not disclose the size of its stake.
Poulina has a market capitalisation of some $745m. Just 10 per cent of the company is listed on the Bourse de Tunis.
The group operates in the building materials, packaging and retail sectors.
Abdelwahab Ben Ayed, chief executive officer of Poulina, says: "We are very happy to welcome Actis as our largest international shareholder. We look forward to working with them as we develop the structure and reach of the group."