Two days after the dismissal of Glenn Roeder, West Ham's caretaker manager Trevor Brooking saw his reshaped side - 4-3-3 as opposed to Roeder's favoured 4-4-2 - outclass the Bantams for long spells but fail to put the Yorkshireman to the sword.
Three forwards - Defoe, David Connollly and Neil Mellor, making his first start at Upton Park - all missed good opportunities to put Bradford out of sight before half-time in front of a vocal and always encouraging crowd of 30,370.
Yet the visitors wasted one of the best chances of the first half when Ebbs prodded his shot wide from 12 yards and they squandered other useful openings in a scrappy second half.
Bradford, beaten at home by Gillingham on Saturday, looked as if they might capitulate early on as Michael Carrick eased his way back into the fold on the right of a midfield trio that included Robert Lee and Matt Etherington, with latest signing Kevin Horlock slotting in on the left of a back four well marshalled by skipper Christian Dailly.
After playing in both full-back positions as well as centre-back in three of the previous four matches, Tomas Repka reverted to right back, while Ian Pearce partnered Dailly in the centre. Repka soon made his presence felt and after drawing criticism from Bradford boss Nicky Laws for hammering Andy Gray, for which he was booked, his subsequent challenge on Dean Windass forced the striker out of the game early in the first half.
By contrast, the visiting defenders had trouble keeping pace with Defoe, who underlined his quality once again with a typically individual goal in the 32nd minute. Cutting in from the left at pace, Defoe brushed aside his markers before thumping a low, right-footed shot inside the far corner of the net from the edge of the box.
He was unfortunate not to have notched his hat-trick before the break and his importance to the side couldn't be underestimated. Connolly, full of impudence, excited the crowd with his clever twists and turns and, in the first half, one amazing run that deserved a goal, only for the crossbar to rescue City.
Mellor, taller and more of a target man, provided some good flick-ons with his head and his additional presence in attack enabled Hammers to retain possession further up field than they had in their three previous games.
Don Hutchison, who was dropped to the bench after a poor display at Rotherham, received a recall early in the second half when he replaced the injured Lee, who hobbled off after coming off worse in a crunching 50/50 challenge with Michael Branch..
By Tony McDonald
2 - The first effort of the game from Jermain Defoe, who finds some space 25 yards out but fires his shot high and wide.
4 - Bradford go close to taking the lead, as Gray collects possession on the edge of the area and turns inside Pearce before planting an effort towards the bottom corner that James saves well.
13 - Repka booked for foul on Windass.
15 - Connolly's clever flick from Mellor's pass releases Defoe, who tries to turn Jacobs but sees the defender divert the ball wide for a corner.
18 - Carrick's superb turn in the centre of the field allows him space to shoot from the edge of the penalty area. His shot is deflected into the path of Mellor, who seems set to stroke the ball home but somehow slides his effort wide of the target.
21 - Etherington's 25-yard stinger is comfortably held by Bradford keeper Paston.
24 - Substitution for Bradford City, Standing replaces Windass.
32 - GOAL! After a fairly quiet spell, Hammers finally make the breakthrough, thanks to a piece of magic from who else but Jermain Defoe! The England under-21 striker collects a pass from Horlock on the left hand touchline, turns between two defenders and then cuts across the field, jinking past three more opponents before firing a stunning effort into the far corner of the net from 25 yards out. West Ham United 1 Bradford City 0.
34 - Defoe almost makes it two, as he collects Mellor's flick-on with his back to goal before sending in a low left-foot shot that Paston does well to hold.
35 - Horlock booked for foul on Francis.
42 - Hammers go close again, and again it's Defoe who is traumatising the Bradford defence. Repka's long clearance drops nicely for the youngster, who turns past Wetherall before unleashing a blistering shot that Paston palms on to the post and away for a corner.
44 - Bradford waste a glorious chance to equalise on the stroke of half-time, as a neat passing move releases defender Edds, who has only James to beat but strokes his shot inches wide of the post.
Added time: 2 minutes.
45 - Connolly, fairly quiet up to now, bursts into life as he collects on the halfway line and surges towards goal, cutting inside a defender in the area and firing in a left-foot shot that clips off the crossbar.
Half-time: West Ham United 1 Bradford City 0.
48 - After coming off second best in a 50/50 challenge with Branch, Robert Lee limps off with what looks like a knee injury.
49 - Substitution for West Ham, Hutchison replaces Lee.
51 - Another magical piece of play from Carrick sees him escape two opponents, and an inch-perfect pass releases Etherington, who is denied a first goal in Hammers colours by the legs of Paston.
54 - A rare chance for Bradford, as Branch latches on to a long pass and bears down on James, but scuffs his shot weakly wide.
58 - Bradford are beginning to make more of a fight of it, and Gray's dipping 25-yarder is tipped over the bar by James.
62 - Almost an embarrassing moment for James who, receiving a back-pass from Dailly, is unaware of the striker closing in on his blind-side, and takes a touch before hurriedly scuffing the ball straight to Standing. The Hammers keeper thankfully redeems himself by tipping the resulting shot over the bar.
69 - Substitution for Bradford, Wolleaston replaces Branch.
75 - Edds booked for foul on Defoe.
Added time: 2 minutes.
90 - Hutchison's long clearance releases Defoe but, as keeper Paston strangely rushes out of his area, the striker scuffs his attempted lob and a defender clears.
Full-time: West Ham United 1 Bradford City 0.