"Global demand for food, feed, fiber and fuel reinforces the need for agricultural productivity, and Dow AgroSciences is well positioned as a technology leader to provide solutions," CEO Jerome Peribere said in a statement.
The company in recent years has been evolving from a maker of herbicides and pesticides into a biotechnology firm using genetics to develop products that protect crops and improve yields.
Dow AgroSciences is in the process of filling the 350 new positions, many of which will have science and technology responsibilities.
Even before the expansion, the company was a huge local employer, with more than 1,000 of its 5,000 workers based at the northwest-side headquarters.
Dow AgroSciences, a unit of Michigan-based Dow Chemical Co., has turned in record performance this year. Sales in the first half of the year increase 26 percent, to $2.7 billion, while operating earnings rose 36 percent, to $666 million.