Figures released by Childline show that more than 1,000 counselling sessions were provided to youngsters worried about their grades in the last financial year, a rise of more than a fifth (21%) over the last two years.
The statistics come the day before teenagers across England, Wales and Northern Ireland receive their A-level results, with many relying on achieving particular grades in order to secure university places.
In total, Childline, which is run by the NSPCC, delivered 1,133 counselling sessions to youngsters specifically worried about their exam results in 2016/17.
Of these, over a quarter (28%), took place in August last year - the month in which A-levels and GCSE results are published.
There has been a sharp rise in the number of counselling sessions for 16-18-year-olds - those teenagers most likely to have taken major exams, Childline said.
It added that young people had expressed disappointment in themselves or worries that their grades might affect their choice of university or college.
Others were concerned about their parents' reaction to their results.
Peter Wanless, NSPCC chief executive, said: "Waiting for exam results can be an anxious time for young people and can leave some struggling to cope.
"Pressure to achieve good grades and worries about securing further education places and jobs can be too much for some teenagers to deal with on their own.
Dame Esther Rantzen, Childline's founder and president, said: "Young people need to remember that getting good exam grades is not a make-or-break moment and, whatever your results, there are options and opportunities to make a great future for yourself.
"This is proved by all the successful people who have made their way in life despite being nowhere near the top of their class.
"The important thing during exam results season is to stick together as a family and be as supportive and encouraging to the person waiting to receive their grades and then planning their next steps.
"And if they are reluctant to open up about how they are feeling or what they want to do then Childline is always ready to provide help and advice."