Out of one lakh employees, India accounts for over 75 per cent of the workforce.
"We had 175 employees in 1994 and are proud to have grown to 1,00,000 in just 16 years," Cognizant President and Chief Executive Officer Francisco D'Souza said.
Asked about the hiring plans in the coming months, the company declined to comment.
"It took us 12 years to reach the first 25,000 associates, while it took us just 12 months to add the recent 25,000 associates to reach the 1,00,000 employee milestone," he added.
In the year from October 2009 to September 2010, the company saw a net addition of over 27,500 employees.
Cognizant, which has presence across North America, Europe, Asia, South America, and Australia, hired its 100,000th employee in the US.
The company has more than 16,000 people in North America and 3,600-plus employees in Europe (of which 2,500 are in UK and over 1,100 employees in Continental Europe).
In order to commemorate this milestone, Cognizant will plant one lakh trees around the world to individually honour its each employee and to support the cause of a greener environment.
"Over the years, Cognizant has been able to not only attract the best talent, but also provide exciting career opportunities with rapid advancement," Cognizant Chief Operating and Financial Officer Gordon Coburn said.