The group has signed a preliminary agreement to offload Lekolar to Swedish investment company Nalka Invest.
The deal, which is subject to regulatory approvals, will see 3i generate proceeds of around £33m.
The private equity house led a buyout of Lekolar in February 2007.
Lekolar supplies educational and learning material, furniture, toys, stationery, arts and crafts and playground materials to pre-schools and secondary schools in the Nordic region.
The company is headquartered in Osby, Sweden, and has a purchasing office in Shanghai, China. It employs around 280 people.
Previously owned by Procuritas, Lekolar sells a variety of products, including wooden railways, dolls, games and puzzles, bicycles and crayons.
London-headquartered 3i also owns OneMed Group, a medical supplies distributor in Northern Europe, in Sweden.
Other recent 3i activity has included the acquisition of assets including Belfast City Airport from Eiser in December, a €150m (£127m) investment in French consumer healthcare business Ponroy Sante Group, and the £45m sale of a minority stake in promotional products company Polyconcept.