Practising yoga for as little as three months reduced symptoms of fatigue and inflammation that followed radiotherapy in a group of patients.
On average, fatigue was reduced by 57% and inflammation by up to 20% after six months.
"This showed that modest yoga practice over a period of several months could have substantial benefits for breast cancer survivors," said study leader Professor Janice Kiecolt-Glaser, from Ohio State University in the US.
She added: "We also think the results could easily generalise to other groups of people who have issues with fatigue and inflammation."
The findings are published in the latest edition of the Journal of Clinical Oncology.
Chronic inflammation is linked to numerous health problems, including heart disease, diabetes, arthritis and Alzheimer's, as well as effects of ageing such as frailty and functional decline.
A total of 200 women aged 27 to 76 took part in the study having undergone surgery or radiotherapy two months to three years earlier. One group was offered 90-minute yoga classes twice a week for three months, and encouraged to practise at home.
Immediately after the sessions ended, tests showed levels of pro-inflammatory signalling molecules were significantly lower in women who had attended. After another three months fatigue levels were 57% lower in the yoga group and inflammation was reduced by between 13% and 20%.