Harrison helped guide Leicester to the Premiership title in the 2021-22 season and he will join England on June 1st.
England men's sevens head coach Tony Roques (44) will also come on board to work with the team as their contact and skills coach during the preparation and training camps.
"Tom is an excellent coach and will have a real impact in area that will be fundamental to us as a team," Borthwick said in a statement.
"Leicester's scrum is renowned across Europe and Tom has played a leading role in that success. I have full confidence in him and I am very happy that he will be joining England.
"Tony has an extensive background in Sevens and is an experienced, specialist contact and skills coach. Individual skill emphasis will be an important part of our work."
The RFU said Richard Wigglesworth (39) will lead the attack coaching and kicking strategy while Kevin Sinfield (42) stays on as the defence coach and Aled Walters heads strength and conditioning.
"Richard has a proven track record as a player and a player coach... He has played at Rugby World Cups and has coaching experience in 2019," Borthwick added.
"Along with Kevin and Aled, I am pleased with the balance and wide range of experience that the coaching staff will have."
England begin preparation camps next month ahead of four summer series fixtures against Wales, who they play twice, Ireland and Fiji.
England will take on Japan, Argentina, Samoa and Chile in Pool D at the World Cup in France which kicks off in September.
