US firms doubled their investment here to nearly $18bn (€13bn) in the first half of the year.
The 49pc increase puts Ireland on the same level as Canada and the UK, according to a new report from the American Chamber of Commerce.
US firms employ just under 100,000 people in Ireland with many attracted by our low corporation tax.
In the past week, Twitter became one of a number of technology companies operating here including Google, Intel and Microsoft but many others like Pfizer and Abbot operate in the pharmaceutical sector.
Investment from the US is now worth $190bn and has grown five fold in the past ten years.
The multinational sector also fuels exports which analysts believe is a key driver of growth in the Irish economy.
According to the figures, multionals now account for one quarter of Irish Gross Domestic Product.