The 36-year-old, who was promoted to the West Brom board as legal director/secretary in December 2010, has been seconded to the role to succeed Dan Ashworth, who will leave this summer to become the Football Association's new director of elite development.
Garlick will now work closely with Ashworth during a handover period to ensure the club are prepared for the summer transfer window.
Garlick's appointment follows a similar pattern to that of Ashworth, who was also promoted from within in a designate capacity in December 2007. He will be responsible for the first team, player recruitment, medical services and Academy.
Chairman Jeremy Peace said: "This is an important appointment for the club."
"We decided to recruit an individual with a current working knowledge of the English game. Therefore we conducted an extensive search in the UK to benchmark all possible candidates to replace Dan.
"As the sporting & technical director role is not yet firmly established in this country, the fact Dan's notice period runs until the summer has given us the opportunity to research a wide range of people with a variety of footballing skill sets.
"We have had Richard in mind since the start of the process and after completing our research, he emerged as the strongest candidate."
Garlick was on Rotherham United's books between the ages of 14 and 18 but after missing out on a professional contract opted instead for a career in the legal profession.