Newly-signed 2021 Tech3 KTM MotoGP riders Gardner dropped the lead to Fernandez midway during the 22-lap competition, but managed to repass the Spaniard to maintain his second consecutive victory in the intermediate course.
At the beginning of the race Gardner pulled away from pole position, using a struggle involving Fernandez and Bo Bendsneyder to escape the front.
For the first half of this race, both Ajo KTM riders circulated the trail over half a second of one another, with Bendsneyder not operating much behind in the last podium spot.
Finally, on lap 12, Fernandez made the movement that was in the making for some time, outbraking his experienced team-mate into Turn 1 to catch the lead.
The struggle for success was far from over yet, with Gardner maintaining Fernandez honest since they started withdrawing from the remainder of the area.
With three laps to go, Gardner seemed to play behind Fernandez since they braked to the opening corner, just for your 23-year-old to dip down the interior and also make the race-winning move.
Once again in the guide, Gardner immediately assembled a buffer of 0.6s before doubling this edge on another tour to begin the last lap with a benefit of over another.
Fernandez had no response to Gardner's speed on the last lap, the Australian easing into another career win in Moto3.
Petronas Sprina's Xavi Vierge finally claimed third position following emptying Bendsneyder on lap 16, together with VR46's Marco Bezzecchi - that jumped from 10th to sixth on the opening lap - additionally passing the SAG rider to secure fourth and lessen the points reduction to the Ajo duo.
Augusto Fernandez was categorized fifth on the direct Marc VDS bicycle, whilst Bendsneyder finally finished two seconds off the podium in sixth.
Qatar and Doha winner Sam Lowes (Marc VDS) fell to 12th in the opening laps but recovered to finish , making the most of many events facing him.
Intact GP's Marcel Schrotter, Honda Team Asia's Somkiat Chantra and American riders Joe Roberts (Italrans) completed the top 10, the last-named climbing up the sequence in the next half of this race after falling to 17th at a stage.
A stunt after Fabio di Giannantonio dropped off his Gresini Kalex into Turn 1, carrying a innocent Hector Garzo (Pons Kalex) with him. This is the second crash involving the two in an area of a month, following both also came together in Le Mans in May.