The figure accounts for 8% of its US workforce and 6% of its total staff worldwide. The company will maintain 30 offices in the US and other countries.
The consultancy said the job cuts reflect a contraction in its business consistent with the downturn in the general economy.
The cuts coincide with a fresh wave of redundancies announced yesterday by Rapp Collins Chicago, TBWA\Chiat\Day New York and DraftWorldWide New York.
Jack Morton is part of Interpublic's Allied Communications Group of agencies.