The deal, if approved will complete by the end of summer, and will take the form of a voluntary public takeover for all outstanding shares offering €6.75 in cash which would value the deal at €75m.
NTT Com has got the backing of several key members of the Integralis board and needs 75% to agree to deal which also goes before the German Federal Supervisory Authority.
In a statement, Akira Arima, senior executive vice president of NTT Com, said that the enterprise security expertise would be "extremely valuable for many of our customers."
After the deal Integralis will form a global security division for NTT Com that will have access to the Japanese company's customer base.
"For Integralis, this partnership is a fantastic opportunity to stay focused on our core security business and yet pursue growth opportunities around the globe, most notably Asia," said Georg Magg, CEO of Integralis.
One shareholder said that the deal was a surprise because Integralis had been profitable and had "solid margins and revenues".
"NTT Comms seems a strange acquisition because it is a communications company but it does give Integralis the chance to expand into Asia," he said.