The study of more than 2,000 working women in the UK found 47% can't be successful at work while also managing home life.
It showed women are adopting alternative behaviours and appearances to succeed, with almost half, displaying a different persona at work compared to home.
O2 published the research to coincide with their 'Women in the Workplace' campaign, which looks into the pressures and experiences of women at work.
The study found there is a "desperate need" to help increase the number of women working at all levels and create an environment in which women can succeed.
One in 10 women said there are no females in senior positions in their company and many women are assuming male characteristics in order to be successful. These include hiding emotions (50%), dressing in a more masculine way (23%) and exaggerating assertiveness (12%).
Telefonica UK HR director Ann Pickering said having a diverse workforce makes "complete business sense".
"While businesses have come a long way from the offices of [T.V series] Mad Men, the reality is that many modern women are still feeling the pressure to conform to outdated stereotypes."
Wake-up call
The study showed more than a third of women (37%) said they have experienced workplace discrimination from both men and women. And one in 10 admitted a male-dominated culture exists at their company, which prevents them from reaching the next level in their career.
"Employers must try and create an environment where all employees feel comfortable. This makes perfect business sense," said Pickering.
"These results should act as a wake-up call for businesses to ensure they don't miss out on the valuable contribution that women can make to their organisations.
"Through a number of simple measures, such as providing better flexible working, mentoring or training, businesses can ensure they help all their people to achieve their potential regardless of the stage of their career or gender."
