The firm said that the purchase would enable it to expand its products and services in the oil and gas industries in which Hillfoot specialises.
MMG is the UK’s largest independent steel stockholder and processor of both general steel and specialist metals.
Chief executive Graeme Hill said: “Hillfoot Steel Group has an outstanding reputation and is renowned for the high quality of its products, services and people.
“This acquisition is further testimony to our ongoing plans to build through organic growth and the acquisition of businesses that share our strategic outlook, ambition and service delivery.”
Hillfoot has 187 staff with an annual turnover of £43 million.