Pahl joined AMV eight years ago and has led the Omnicom agency’s BT account for most of his tenure. He became managing partner in October last year.
Meanwhile, chief innovation officer Jonny Spindler has become chief operations officer. He started at AMV as innovation director in 2010. Pahl and Spindler will report to chief executive Ian Pearman. All department heads will now report to Pahl.
Pearman said: "Justin is a living, breathing embodiment of what AMV stands for and has great clarity about how we need to keep evolving the business. "Jonny has been a fantastic change agent, and making him a core part of the management team will multiply the speed and impact of change we can achieve."
As part of the changes, AMV has also promoted Claire Hollands, Katy Talikowska, Jo Verdult and Chris Taggart to managing partners. Arscott joined AMV in 2005 and became managing director in 2012. He leaves at the end of the year to launch South African tech company Names & Faces in the UK.