Hanson joined the German web-to-print giant last November, becoming the first person to hold that level of role in the UK.
Prior to FlyerAlarm he held senior roles at Albumprinter and CeWe.
In a statement, FlyerAlarm said Hanson had taken the decision to leave for personal reasons. The firm’s chief executive Farid Mahmood thanked him for his contribution to the company.
“Keith has made a significant contribution to our operations in the UK and we are sorry he is leaving. We remain committed to providing the UK with the finest services from what is one of Europe’s leading online printing brands,” Mahmood said.
Also in the statement, Hanson said: “I am sorry to be leaving. FlyerAlarm is a vibrant and forward looking company which is a major player in the future of printing.”
FlyerAlarm has not commented on whether it plans to directly replace Hanson, or not.
During Hanson’s tenure the firm launched a number of promotions, including slashing the price of flyers and giving money off vouchers for new customers as part of moves to expand its UK customer base. All its products are manufactured in Germany.
Two months ago Hanson also launched a recruitment drive to expand his team with new marketing and account management positions, including a key account manager to be tasked with targeting “potential large new multi-million-pound clients”.
Privately-owned FlyerAlarm was established in 2002. It is headquartered in Würzburg, Germany and operates in 15 countries across the continent. Group turnover is more than €330m (£301m). The firm does not publicly disclose UK turnover.