The portrait, which is around 1 metre in size, is by artist Jonathan Yeo, one of Britain's leading portrait painters. It shows the 16-year-old Malala doing her homework.
Yeo painted Malala in Britain where she has settled since the attack in her home town of Swat in October. He described the experience as "a privilege".
"Given how much she has already been through and all that she represents to the world, it took a while to adjust to the fact that she is still a very fragile teenager," he said. "Hopefully the painting reflects the slight paradox of representing someone with enormous power and wisdom yet vulnerability and youth at the same time."
The picture forms part of a wider exhibition of portraits by Jonathan Yeo, and is the NPG's first display dedicated to the artist. Other subjects on display include some of today’s leading cultural, media and political figures: Tony Blair, Helena Bonham Carter, Stephen Fry, Kevin Spacey, Erin O'Connor, Grayson Perry and Jude Law.
The show runs until January, when the Malala portrait will be sold to raise money for The Malala Fund, which campaigns for the right for girls to go to school.
Jonathan Yeo Portraits runs at the National Portrait Gallery, St Martin's Place, WC2H 0HE in rooms 41 and 41a until 5 January. Entrance is free.