The probe, launched from the Earth in 2011 to study the giant planet from an elliptical, polar orbit, achieved the milestone on Wednesday when it was about 793 million km from the Sun.
"Juno is all about pushing the edge of technology to help us learn about our origins," said Scott Bolton, Juno principal investigator at the Southwest Research Institute in San Antonio, in a Nasa statement.
The Juno spacecraft will arrive at Jupiter on July 4 this year. It will repeatedly dive between the planet and its intense belts of charged particle radiation, coming only 5,000 km from the cloud tops at closest approach.
"We use every known technique to see through Jupiter's clouds and reveal the secrets Jupiter holds of our solar system's early history. It just seems right that the Sun is helping us learn about the origin of Jupiter and the other planets that orbit it," he explained.
Juno is the first solar-powered spacecraft designed to operate at such a great distance from the Sun.
The four-ton Juno spacecraft carries three 30-foot-long solar arrays festooned with 18,698 individual solar cells.
"Jupiter is five times farther from the Sun than Earth, and the sunlight that reaches that far out packs 25 times less punch," added Rick Nybakken, Juno's project manager from Nasa's Jet Propulsion Laboratory in California.
"While our massive solar arrays will be generating only 500 watts when we are at Jupiter, Juno is very efficiently designed, and it will be more than enough to get the job done," he disclosed.
Solar power is possible on Juno due to improved solar-cell performance and energy-efficient instruments.
The spacecraft is designed in such a way that it can avoid Jupiter's shadow, and a polar orbit that minimises the total radiation.
Over the next year, the spacecraft will orbit the Jovian world 33 times.
During the flybys, Juno will probe beneath the obscuring cloud cover of Jupiter and study Jupiter's aurorae to learn more about the planet's origins, structure, atmosphere and magnetosphere.
The previous record-holder was the European Space Agency's Rosetta spacecraft, whose orbit peaked out at the 792 million km mark in October 2012, during its approach to comet 67P/Churyumov-Gerasimenko.
Prior to Juno, eight spacecraft have navigated the cold, harsh underlit realities of deep space as far out as Jupiter and all have used nuclear power sources to get their job done.