The problem was even worse among retired players with 39 percent saying they were affected.
"Symptoms relating to depression and anxiety are highly prevalent among professional footballers," said FIFPro in a statement as it announced the findings.
"Contrary to popular belief, the life of a professional footballer has some dark sides," said FIFPro's chief medical officer Vincent Gouttebarge who conducted the research.
"Football stakeholders have a collective responsibility to remove the stigma associated with mental illness," he said. "All players, whether active or retired, can learn optimal behaviours and coping skills to manage the symptoms of mental illness."
FIFPro said that 180 active professional footballers took part in its survey.
Twenty-six percent reported suffering from depression or anxiety and adverse nutritional behaviour, 19 percent reported adverse alcohol behaviour, 3 percent said they had low self esteem and 7 percent said they were smoking, FIFPro said. Five percent reported "signs of burnout."
Gouttebarge said the numbers were even higher among former players with 32 percent of the 121 interviewed reporting adverse alcohol behaviour and 12 percent saying they were smoking.
"Once the players stop with intensive physical activities they lose their structured life, their social support by trainers and team mates diminishes, they need to find their place in 'regular' society, and find another occupation," said Gouttebarge.
"Consequently, they are likely to experience some mental health problems during this period.
"When it comes to any health problem, be it physical or mental, over the short or long term, the minimum standard is to raise self-awareness of players about these issues," he added. "They need to be aware of what might occur during and after their football career."
FIFPro said it interviewed players in Netherlands, Scotland, Ireland, Australia, New Zealand and the US.
- Mental Health