J&J Design Office was founded by Japec and Jernej Jakopin in 1983 in Ljubljana, Slovenia. Its first decade was marked by bestselling designs for major sailboat manufacturers such as Elan, Jeanneau, and Bavaria. From 1990 onward, the office was supported by an in-house plug and mould shop, enabling it to provide the full development process—from concept design and naval architecture to engineering, tooling, and prototyping.

J&J began designing powerboats in 1987, and for the past 30 years this has been the firm's primary focus. Extensive research conducted in tank-testing facilities has underpinned much of its work. The introduction of carbon/epoxy technology into production boatbuilding led to the launch of the Shipman Carbon sailboat range in 2002. In 2008, J&J introduced Greenline, its first diesel-electric and fully electric boat range. Today, J&J designs account for more than 1,000 hybrid boats in operation, making it the world's largest hybrid fleet of its kind.

In 2011, J&J developed the first models for the newly established Chinese power catamaran brand Aquila, which has since become the world's largest power catamaran manufacturer. In recent years, the office has also designed vessels for Saxdor, one of the fastest-growing powerboat brands globally, contributed to the BMW/TYDE fully electric foiling project, and developed the Beneteau Group's latest fully electric Island Cruising Concept. Today, J&J's portfolio spans more than 400 production projects for boatbuilders across three continents.