The approval by a NASA team of independent experts came a year ahead of schedule and included several technologies never before used on any satellite or space telescope, officials said.
NASA said the early approval can reduce the risk of increased costs and schedule delays.
The actual hardware and software that will fly on the telescope now can be engineered from working prototypes. The technologies will allow the observatory to look back in time to about 400 million years after the Big Bang, enabling scientists to study the first generation of stars and galaxies.
One example of the new technologies is the telescope's microshutters -- tiny doorways, the width of a few hairs, that will allow scientists to remotely and systematically block unwanted light and view the most distant stars and galaxies ever seen. The telescope will be the first project to employ that technology.
The James Webb Space Telescope is a joint project of NASA, the European Space Agency and the Canadian Space Agency.