NASA released the new images on Wednesday, the birthday of Clyde Tombaugh, the American astronomer who discovered Pluto in 1930.
The pixellated images of Pluto and its biggest moon Charon were taken on Jan. 25 and Jan. 27, from a distance of 203 million kilometres.
"Pluto is finally becoming more than just a pinpoint of light," said Hal Weaver, project scientist for the mission, which is based at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md.
In a statement, he added that the new images show the spacecraft's camera is still working just as well as it did during launch more than nine years ago on Jan. 19, 2006. Since then, it has travelled more than 4.8 billion kilometres.
Much better images are expected from the spacecraft in late spring, when it will be much closer to Pluto. The Hubble Space Telescope has also taken higher-resolution images of Pluto.
New Horizons is scheduled to do a close flyby of Pluto and its moons on July 14.
In addition to Charon, it is known to have four smaller moons, named Nix, Hydra, Kerberos and Styx – all after characters associated with the underworld in Greek and Roman mythology.
Between now and the flyby, the spacecraft's Long-Range Reconnaissance Imager camera will take hundreds of better photos that will be used to correct its course and help it make a more precise approach, NASA says.
Pluto was originally considered our solar system's ninth and most distant planet. But decades after its discovery, scientists found many similar-sized objects in the solar system, including many in the Kuiper Belt beyond Neptune. In 2006, after the launch of New Horizons, Pluto was demoted to "dwarf planet."