Financial details of the new pact were not disclosed.
BT has worked with Syngenta since 2000, managing all aspects of communications including an integrated IP infrastructure to reduce costs and enable expanded collaboration services, the British firm said in a statement.
BT will provide new services like wide area network (WAN) optimisation, wireless local area network expansion, unified communications support and application performance monitoring to Switzerland headquartered-Syngenta under the fresh contract, it added.
"We are pleased to be able to continue our partnership with BT. The continued use of new technology is helping us increase productivity by making our employees more connected," said Martin Walker, Head of Syngenta Business Services.
In India, Syngenta operates two business divisions - seeds and crop protection.
"Syngenta has ambitious growth plans in key regions that are aligned to BT's areas of investment such as Latin America, Asia, Middle-East and Africa. We work hard to help our customers orchestrate their networked IT services across multiple platforms and very diverse geographies," BT Global Services Chief Executive Officer Luis Alvarez said.