Boxall will be responsible for Walker Media's joint team, buying space across TV and digital display. Walker Media created the team and the position of head of screen in February.
Boxall joined Harvest Digital as client services director in October 2011 after nine years at Walker Media.
He joined Walker Media in September 2002 and worked in its TV buying department, before becoming group account director for Dixons and then leading the agency's digital account team for Barclaycard.
Prior to joining Walker Media, Boxall worked at the Manning Gottlieb Media-backed agency The Allmond Partnership, and as an online sales manager at Future Publishing.
Boxall began his career in TV sales in 1989, rising to a group head at Carlton TV, before moving to Future in 1999.
Simon Davis, chief executive of Walker Media, said: "Malcolm's experience in planning, TV buying and digital media makes him the ideal person to lead our screen department as we accelerate our ability to offer joined-up, commercially optimised screen media plans for our clients."
Record left Walker Media in November to join Aegis Media as international trading manager.Follow @MaisieMcCabe