It is the US-based ad agency's second round of job losses in recent months following a similar size layoff in late October.
The agency said the pay cuts are being made to keep redundancies to a minimum and will hit the highest-earning employees hardest.
Arnold is also attempting to ease the blow by paying performance bonuses to remaining employees and those being made redundant with funds from its 2008 profits.
Job cuts will be made only in Boston with no layoffs in the McLean, Virginia or New York offices.
Arnold said that the cuts are "totally based on the economy" but it is rumoured that they are partly attributable to the agency's impending loss of the RadioShack account. Arnold was knocked out of the pitch process last month.
Earlier this month Havas restructured its operations, uniting Arnold and Euro RSCG under a new entity headed by Euro RSCG CEO David Jones.
The newly-created Havas Worldwide houses all the company's creative and digital agencies, representing roughly 80% of Havas' annual revenue, and is designed to provide a more "streamlined" offering.