Research published in BMJ Open reveals participants saw a 58% reduction in anxiety, 57% in depression and 40% in perceived stress.
There was a further decrease in stress, anxiety and depression levels one month after completing the course, suggesting continued practice of the skills learnt.
The benefits were comparable to Improving Access to Psychological Therapies (IAPT) services and face-to-face mindfulness courses despite the expected benefits of group and therapist interaction for recovery.
An individual's ability to access support of their own accord and in familiar surroundings enables them to use the skills learnt more effectively and often to recall them more easily.
Adele Krusche, of the University of Oxford's school of Department of Psychiatry, said:
"The study shows great potential for the role of online technology in delivering mindfulness courses to decrease stress, anxiety and depression.
"This is the first known study to measure how much time spent practicing mindfulness online will bring about a positive change, with more mindfulness practice significantly improving stress, anxiety and depression."
Dr Eva Cyhlarova, Head of Research at the Mental Health Foundation said:
"The concept of mindfulness has really hit the headlines in the last few years. Not only is it seen as an accessible, non-stigmatising way of protecting our wellbeing, but now even more evidence points to its ability to improve people's mental health.
"We hope this is just the beginning of a range of online interventions which are convenient, appropriate and cost-effective in supporting those seeking mental health support."
For more information about the course visit: www.bemindfulonline.com