It is the first company listed on Germany's DAX index of blue-chip stocks to take such a stand, and the measure concerns upper and middle management positions, a statement said.
"Having a greater number of women at the top will quite simply enable us to operate better," chief executive Rene Obermann said. "Taking on more women in management positions is not about the enforcement of misconstrued egalitarianism. It is a matter of social fairness and a categorical necessity for our success."
A study by the DIW economic research institute found that only 2.5 percent of management positions within the 200 biggest German companies are held by women. Industrial giant Siemens is the only DAX company to have a woman on its senior board.
Deutsche Telekom personnel director Thomas Sattelberger noted meanwhile that around 60 percent of business graduates from German universities are women.
Norway has already passed a law to ensure more women have access to senior positions, and France and the Netherlands are mulling similar legislation.
Deutsche Telekom said the ratio would be respected in its operations worldwide, and would be "prepared systematically on the basis of targets governing, for example, the recruitment of university graduates, selection processes, talent pools and participation in executive development programs."
German Family Minister Kristina Schröder told the Financial Times Deutschland newspaper Monday that legally binding quotas for women executives should only be a last resort, but was quoted by the Deutsche Telekom statement as saying the group "is setting a fine example."