The PIC previously held 10.47% in Nampak, according to the company's 2019 Integrated Report.
In a notice issued on the JSE news service, the firm, which is Africa’s largest diversified packaging manufacturer, announced that the PIC's shareholding in the company now amounts to 20.54% of the total issued ordinary shares of the company.
The PIC invests on behalf of the Government Employee Pension Fund, and manages around R2.1trn in assets.
In December, Nampak appointed Erik Smuts as its new chief executive officer to replace Andre de Ruyter, who recently took over as Eskom CEO.
The 2019 annual financial statement of the company, which produces metal, glass and rigid plastic packaging, showed a loss of R390m compared to the previous year's profit of R1.2bn.
Nampak has facilities in 11 countries across Africa, and in the United Kingdom as well as Ireland. In his results presentation in November, De Ruyter said the "majority of regions experienced constrained consumer demand and concomitant pressure on volumes."
Nampak shares were trading at R5.10 at 16:10 on Friday, up 0.99%.
*Compiled by Sibongile Khumalo