Last year's Newcombe medal won the WTA Elite Trophy in Zhuhai, another grass singles title in Nottingham, and four doubles titles – including his first Grand Slam alongside American Coco Vandeweghe in New York.
Barty racked up 46 wins for the season, reaching the Sydney final, semifinals in Strasbourg, Montreal and Wuhan, and making the fourth round of his career at the US Open in addition to his two successes.
De Minaur could not be denied after being named ATP's Newcomer of the Year after his meteoric rise from No.208 to a 31st place in the 2018 ranking.
The 19-year season began with races for the Brisbane semifinals and the Sydney final that earned the teenager a Davis Cup debut where he took the world number 4 Alexander Zverev to five sets.
He also reached the final in Washington before completing his year with a second place finish at the Next Gen ATP Finals in Milan.
US Open finalist John Millman, who rose to No.33 in the world after his stunning Roger Federer victory at Flushing Meadows, and wheelchair champion Dylan Alcott, who clinched the sixth Grand Slam title this year, others named for the top gong on Monday night.
A highlight of the evening at the Crown Casino in Melbourne was the Spirit of Tennis Award presentation to retired ace Casey Dellacqua for his remarkable achievements on and off the court.
Darren Cahill, who led the women's world number 1, Simona Halep, to his grand slam title at the French Open, won the prize for excellence in training.
Full list of 2018 Newcombe award winners:
Newcombe Medal: Ashleigh Barty and Alex de Minaur
Spirit of Tennis: Casey Dellacqua
Excellence in coaching performance: Darren Cahill
Development of excellence in coaching: Stephen Thompson
Female junior female of the year: Destanee Aiava
Male junior athlete of the year: Rinky Hijikata
Most notable athlete with a disability: Archie Graham
Club of Excellence in Coaching: Adon Kronk, Mooloolaba Tennis Club, Queensland
Most excellent tennis club: Henley South Tennis Club, South Australia
Most notable school: Casuarina Street Elementary School, Katherine East, Northern Territory
Excellency in officiating: Simon Cannavan
Prize of voluntary conquest: John Pick
Most excellent professional tournament: 2017 Apis Canberra International, Canberra, ACT
Highest Australian qualifying tournament: AGL Loy Yang Traralgon International, Victoria
Most excellent 35+ senior tennis: Peter Froelich.