The aim of the merger is to create an "unmatched leader" to serve clients that are transforming into digitally-driven businesses in a marketplace that is undergoing a rapid pace of change.
SapientNitro chief executive Alan Wexler will become chief executive at newly formed SapientRazorfish, while current Razorfish chief executive Shannon Denton has been appointed chief strategy officer for the merged company.
Chip Register will continue in his role as chief executive of Sapient Consulting and will also assume the position of co-CEO of Publicis.Sapient alongside Wexler.
Nigel Vaz will lead both EMEA and APAC at a Publicis.Sapient level, which involves running SapientRazorfish, Sapient Consulting and Digitas LBi across EMEA and APAC
As part of the changes Alan Herrick will take on the chairman role at Publicis.Sapient, which will focus more on strategy and market issues.
Herrick said: "We have had great success in helping our clients with their transformation programs since the formation of Publicis.Sapient in early 2015.
"By creating SapientRazorfish, and by implementing a more integrated management structure, we are combining the very best digital and technology assets in one combined unit.
"SapientNitro and Razorfish have been clear market leaders since the invention of digital. To now bring them together builds on the great success we have seen in many recent collaborations with clients."
Parent company Publicis Groupe believes coupling SapientRazorfish with the Publicis.Sapient platform – which includes Sapient Consulting and DigitasLBi – will provide it the unique "ability to help its clients define their digital business strategy and execute rapidly across complex organisations".
Maurice Lévy, Publicis Groupe's chairman and chief executive added: "When we formed Publicis.Sapient we integrated the strongest set of capabilities in digital, consulting and technology amongst any of our peer group.
"We are now taking this next, important step, to further integrate these formidable assets. SapientRazorfish is a powerful new entity in the marketplace uniquely combining customer experience strategy, omni channel commerce, and technology deployment to create a new breed of digital transformation partner pointed at today’s most critical client need – reshaping their businesses for the future.
"I am confident that Alan and Chip, together with the new Publicis.Sapient structure and management in place, will continue to drive digital revenue to our goal of 60% by 2018."