The hosts capped a strong start with Ephron Mason-Clark's goal, and ended the match as a contest eight minutes from the end through Nicke Kabamba.
Between that, Jamie Stott had been sent off for two bookable offences, with the game offering barely any redeeming features for the away side.
After coming into the season on a wave of positivity, it was typical Halifax Town to make a false start.
Tylor Golden, Stott, captain Tom Clarke, Jamie Cooke, Jordan Keane, Mani Dierseruvwe and Sam Smart all made their debuts for Town, as did Millington as manager, and he cut a frustrated figure on the sidelines.
He would have expected and will now demand much better.
The Bees were buzzing in the early stages, forcing Halifax back and firing crosses into the visitors' box.
The offside flag spared Jack Senior's blushes when his header only found Mason-Clark. He played through Kabamba, who finished well but was offside.
It was a warning Town didn't heed though as, minutes later, Mason-Clark was played through and produced a lovely finish, and this time the flag stayed down.
Sam Johnson then had to be alert to save Ryan De Havilland's shot and then tip over a bouncing ball in the box as Barnet remained in the ascendancy.
The Shaymen simply hadn't got going, not imposing themselves on the game, not good enough on the ball or aggressive enough off it.
The best the away side could manage from an uninspiring opening half-an-hour was a tame shot well wide by Cooke.
The longer the opening half went on, you were losing count of how many cross field passes by Halifax had been over hit or misdirected.
The Shaymen did grow into the half after their desperately sluggish start, with Dierseruvwe seeing a goal ruled out for offside, thwarted by an excellent tackle within shooting distance and then firing wide from 20 yards.
Barnet's earlier effervescence had deserted them by half-time, with Town now competing much better and attacking more frequently, but it had taken a long time in coming.
Halifax's midfield three had been overrun earlier in the half, but gradually wrestled some influence, as did Dierseruvwe, who looked a threat, but it still needed more from the visitors.
Halifax at least started the second-half more on the front foot than they had the first, but still lacked the quality to hurt the hosts.
Town fans protested in vain for a back pass to the Barnet keeper from a Harvey Gilmour cross following a strong run by Dierseruvwe; it was incrementally better from Halifax, but they were still yet to test the Barnet keeper midway through the second-half.
By which point Stott had been shown a second yellow card on a debut to forget for the centre-back, badly damaging what hopes there were of a Town leveller.
Substitute Luke Summerfield's deflected cross finally brought Laurie Walker into action, with the ten men at least showing some spirit in their attempts to equalise, but they also looked vulnerable to another Barnet goal.
That arrived when Kabamba sprung the offside trap and finished coolly in the searing heat to condemn Town to the defeat which looked on the cards for most of the contest.
Only the crossbar prevented Barnet from a late third with a spectacular effort from range.
Barnet: Walker, Wynter, Collinge, Diarra (Beard 70), Okimo, Gorman, Pritchard, De Havilland, Mason-Clark (Smith 88), Shields (Hall 80), Kabamba. Subs not used: Thomas, Callan.
Scorers: Mason-Clark (14), Kabamba (82)
Shots on target: 6
Shots off target: 5
Halifax: Johnson, Golden, Stott, Clarke, Senior, Keane, Cooke (Summerfield 69), Gilmour, Smart (Alli 60), Slew (Harker 76), Dierseruvwe. Subs not used: Minihan, Hunter.
Shots on target: 1
Shots off target: 4
Attendance: 1,286 (187 away)
Referee: Robert Massey-Ellis
Town man of the match: Mani Dierseruvwe, was a threat up front and tried to make things happen, could have just done with more support.