The merger only affects the UK arms of the two companies and not the parent organisations.
Kettering-based Lappset UK distributes mainly wooden play equipment. Playworld Systems Europe specialises in metal equipment. The management said it hoped that the merger would give them wider scope for sales.
The combined Lappset Playworld will be run by managing director Chris Jones. He said: "It was a very good fit for both companies. A lot of customers have a list of suppliers that can provide wooden equipment and a list for metal equipment. Now we can be on both."
Jones said there had also been a geographical split: "Areas like the West Midlands tend to specify metal equipment. Other places specify wood. We want to provide a one-stop shop for buyers."
He added that the trend was now towards natural play equipment, although metal equipment was always used in areas such as skateparks.
Lappsett chairman Johanna Ikaheimo said the merger would help both firms to grow outside the UK. Playworld Systems chairman Dale Miller said the heritage of the parent companies would not be lost.