Around a billion people around the globe suffer from the condition, also known as hypertension, the United Nations health agency said.
The condition is one of the most important contributors to heart disease and stroke, which together make up the world's number one cause of premature death and disability.
Researchers estimate that high blood pressure contributes to nearly 9.4 million deaths from cardiovascular disease each year, the WHO said.
It also increases the risk of conditions such as kidney failure and blindness.
"Our aim today is to make people aware of the need to know their blood pressure, to take high blood pressure seriously, and then to take control," the WHO's director general, Margaret Chan, said in a statement.
Detecting high blood pressure is the first step in preventing and controlling it, the agency underlined.
People can cut the risks by consuming less salt, eating a balanced diet, engaging in regular physical activity, avoiding tobacco use and cutting down on drinking, it said.
According to WHO data, the prevalence of hypertension is highest in Africa, where it affects 46 percent of adults, while the lowest prevalence is in the Americas, where 35 percent have it.
High-income countries overall have a lower prevalence of hypertension, 35 percent of adults, than their low- and middle-income counterparts, where 40 percent are affected.
That difference is thanks to targeted health policies and better access to care, the WHO said.