The striker looks determined and as sharp as ever following his summer disappointment with England and struck a typical Defoe goal to open the scoring on a windy night in Albertville.
With 35 minutes on the clock, Danny Murphy fed the ball into the 23-year-old and he worked a yard of space on the edge of the box before rifling into the bottom corner.
McKenna, on as substitute, then grabbed his chance with both hands with just three minutes left - arriving with perfect timing to nod home Reto Ziegler's cross.
Summer arrivals Dimitar Berbatov and Benoit Assou-Ekotto both started as we kicked-off our pre-season campaign against the runners-up in Ligue 1 last season.
Berbatov partnered Defoe up front, Assou-Ekotto started at left-back with Edgar Davids captaining the side and lining-up alongside Danny Murphy in midfield.
Bordeaux are slightly further down their pre-season path and started well, Ducasse cracked the crossbar after nine minutes but Radek Cerny's goal wasn't threatened further.
We were starting to find our collective feet when Defoe opened the scoring and the livewire forward almost caught out Valverde with a cheeky lob from the half-way line that drifted just over.
Bordeaux levelled in the final seconds of the first half as Darcaeville combined with Marange and Micoud provided the finish from close range.
Berbatov went close from 20 yards at the start of the second half before the first substitutes as O'Hara and Ziegler replaced Defoe and Routledge, Martin Jol switching to a 3-5-1-1 system.
Davids forced another opening for Berbatov with 20 minutes left, well saved by Valverde, before the Bulgarian international and Phil Ifil were replaced by Lee Barnard and McKenna.
It didn't take long for tigerish midfielder and reserve regular McKenna to make his mark as he guided Ziegler's cross back across Valverde and into the far corner for the winner.
5mins: Routledge met Reid's deep cross with first-time volley but ball zipped wide.
8mins: Dawson vital interception from Menegazzo's low cross, ball slid inches wide of own post.
9mins: WOODWORK. Ducasse piledriver from 20 yards clipped the top of the crossbar.
19mins: Micoud 22-yard free-kick curled a couple of yards over.
21mins: Darcaeville free-kick swung in from left just evaded packed penalty area.
25mins: Our best move so far, Reid involved a couple of times and eventually released Ifil down the right, early cross met by Defoe but not enough power on shot to trouble Valverde.
35mins: GOAL. Defoe gets the opener, a typical strike - Murphy played the ball into his feet on the edge of the box and he worked a yard before drilling home low past Valverde into the bottom corner.
Bordeaux 0, Spurs 1
38mins: Defoe cheeky effort from near the half-way line drifted just over.
44mins: With only a few seconds left, Micoud managed to get on the end of Marange's cutback and slot the ball into the corner from six yards.
Bordeaux 1, Spurs 1
Half-time: Bordeaux 1, Spurs 1
52mins: Balde managed to toe poke Francia's corner towards goal but Cerny made comfortable save.
59mins: Berbatov latched onto a misplaced defensive pass and lashed just wide from 20 yards.
60mins: SUBS. O'Hara and Ziegler for Defoe and Routledge.
70mins: SAVE. Driving run from Davids, one-two with O'Hara, dribbled past two defenders and allowed ball to run to Berbatov supporting from the left, took shot first time but Valverde smothered well.
71mins: Ifil darted in from right-back, snapshot into side-netting.
79mins: SUBS. McKenna and Barnard for Ifil and Berbatov.
85mins: O'Hara, playing just behind striker, clever cross in from right that Barnard tried to reach but defender did enough to block him out.
87mins: SUB. Lee for Murphy.
88mins: GOAL. Ziegler deep cross from left picked out McKenna at far post, floated perfect header back across Valverde and into the far corner.
Bordeaux 1, Spurs 2
Full-time: Bordeaux 1, Spurs 2
Line-ups: Bordeaux (squad): Valverde, Dos Santos Souza, Jurietti, Alonso, Darcaeville, Francia, Valencia, Micoud, Laute, Rame, Baysse, Faubert, Ducasse, Balde, Bregerie, Marange, Cid, Obertan, Tremoulinas.
Spurs: Cerny, Ifil (McKenna, 79), Assou-Ekotto, Davids, Dawson, Gardner, Routledge (Ziegler, 60), Murphy (Lee, 87), Berbatov (Barnard, 79), Defoe (O'Hara, 60), Reid. Subs: Davenport, Fulop, Huddlestone.
Jermain Defoe got straight back on the goal trail as Kieran McKenna's late header toppled Bordeaux in Thursday's friendly in France.