The NCS first launched in 2011, initially to a few thousand young people, but provision has been expanding each year, with the government setting aside around £1.2bn to deliver NCS up to 2020.
An evaluation report into 2016 programmes delivered in the summer and autumn found that, overall, NCS participants were positive about the experience and the staff who delivered their programme.
Participants agreed with a range of positive statements about the programme and the majority of participants said they would "definitely" recommend NCS to other 16- and 17-year-olds.
More than 90 per cent of those who took part in both the NCS's summer and autumn programmes gave it an overall score of six or more out of 10.
Meanwhile, 94 per cent of summer participants and 88 per cent of autumn participants said they were proud of what they had achieved by taking part.
The evaluation also reported that young people's confidence, ability to get along with others and their life satisfaction had improved following participation.
There were also indications that the scheme had improved social cohesion, with the proportion of young people who feel comfortable with a friend or relative dating someone from a different race or a person of the same-sex increasing after participation in the programme.
The evaluation estimated that every pound spent on the summer programme delivers economic and volunteering benefits worth £1.79, while every pound spent on the autumn programme generated £2.21 of benefits.
"The value-for-money analysis consistently demonstrated monetised benefits that were greater than costs," said the evaluation report.
"This positive assessment remained when considering alternative approaches; when using different assumptions relating to the possible persistence of effects; and when undertaking a number of sensitivity analyses."
The report adds that a follow-up study of the 2013 summer programme reported that many of the positive impacts of NCS had been "sustained over the longer-term".
However, the evaluation confirmed that significantly fewer young people took part in NCS in 2016 than the government had initially hoped.
A total of 92,715 young people joined NCS programmes in 2016, compared to the 150,000 envisaged by the government back in 2013.
Earlier this year, it emerged that participation targets for 2020/21 have been scaled back from the initial goal of 360,000 participants that year to 247,000.
Michael Lynas, chief executive of NCS Trust, said: "When NCS was launched, our goal was to help unlock the potential of our country's young people, while also creating a more integrated, engaged and mobile society.
"Some 400,000 young people have now taken part in NCS and we continue to see the transformational effect the programme has on individual lives, and the families and communities around them.
"It is gratifying to have this evaluation from DCMS not only confirm this, but also highlight that the impact of the programme year on year continues to improve - both for the young people we serve and for society as a whole."