ECOS was established from the merger in 1995 of the consulting companies Gofas & Associates S.A. and ECOS Consulting Ltd.

Gofas & Associates S.A. was founded in 1960 and specialised in the design of large water-related projects in Greece such as dams, water supply and irrigation schemes, wastewater treatment etc.

ECOS Consulting Ltd. was founded in 1989 by ADK Consulting Engineers S.A. of Greece, a consulting engineering firm in the transport sector, and DELFT HYDRAULICS (now DELTARES) of the Netherlands, a foundation dedicated to the management of water resources. ECOS Consulting Ltd. provided specialized consulting engineering services in the water sector in Greece.  

ECOS Consulting S.A. has since acquired diverse expertise through showcase projects in the water sector in Greece, including final design of significant infrastructure and technical assistance in the water sector.