Arsenal grab London bragging rights
At the Emirates Stadium there was cause for concern for England boss Roy Hodgson, ahead of the World Cup qualifiers against Moldova and Ukraine, as midfielder Jack Wilshere hobbled off before half-time.
But that worry was largely forgotten by the full-time whistle as home boss Arsene Wenger, yet to make a star signing in the transfer window, expressed his delight on the touchline.
Spurs may have been without Real Madrid-bound Gareth Bale, but their £100million-plus spending spree saw plenty of talent in Andre Villas-Boas' match-day squad, with £26million man Erik Lamela starting on the bench following his transfer from Roma that was finalised on Friday.
Arsenal, having so far brought in only two free transfers, earned the bragging rights after Giroud tucked home his fourth goal in five appearances to settle an entertaining, but also heated, contest.
There was a bright start by the hosts, and Santi Cazorla forced a fine early save from Hugo Lloris with a 20-yard curling free-kick.
The Spaniard then had another go from a more central position after Theo Walcott was upended by Mousa Dembele, and this time his low effort went under the wall, bobbling just wide.
Spurs settled and Roberto Soldado, the £26million striker signed from Valencia, had a close-range shot blocked by Per Mertesacker.
Arsenal, though, swept into the lead after 23 minutes, with a swift counter from Aaron Ramsey and Tomas Rosicky seeing the ball played out to Theo Walcott down the right.
The England forward cut a pass towards the six-yard box - where Giroud arrived ahead of Spurs captain Michael Dawson at the near post to convert a lovely left-footed finish.
Arsenal looked to quickly further extend their advantage, with Walcott's angled drive beaten away by Lloris. Wales midfielder Ramsey then crashed a shot horribly over the bar after being set up just inside the area by Cazorla.
As the half-hour mark passed, it continued to be one-way traffic.
Lloris came rushing out of his area to slide in on Walcott and got his toe to the ball as the Arsenal forward tumbled - with the home fans screaming for what could have been a red card from referee Michael Oliver, whose decision was backed up by television replays.
Arsenal were forced into a change just before half-time, when midfielder Wilshere signalled he was unable to continue and hobbled off, to be replaced by Mathieu Flamini, the former Gunner rejoining his old club on a free earlier this week.
Spurs made a lively start to the second half, forcing a couple of corners from which they failed to really test the Arsenal defence.
Flamini, released by AC Milan at the end of last season, was cautioned for a sliding challenge on Danny Rose. Nacer Chadli's free-kick, though, flew high into the Clock End.
Arsenal were struggling to find fluency, as the tempo was interrupted by a string of niggly fouls from both sides.
When Giroud was played in by Cazorla at the edge of the Spurs penalty area, his low shot deflected goalwards and was pushed just wide by Lloris.
Spurs boss Villas-Boas looked to liven up his attack with 20 minutes left as Dembele was replaced by Jermain Defoe.
Arsenal were the next to threaten though, Lloris racing out quickly to beat Walcott to the loose ball again, this time with his hands.
There was a stoppage as Tottenham midfielder Etienne Capoue - signed from Toulouse in a £9million deal - needed treatment after badly twisting his ankle in a tackle with Cazorla, and had to be carried off on a stretcher.
Sandro came on, with Townsend also replaced as Lamela made his debut.
Spurs went close to an equaliser when Defoe's shot at the near post was saved by Wojciech Szczesny and the follow-up from Soldado cannoned into Giroud.
At the other end, Walcott's shot was saved by Lloris with substitute Nacho Monreal just unable to get to the rebound.
Spurs continued to push Arsenal back during five minutes of stoppage time, but Wenger's men remained resilient - and jubilant chants of 'What a waste of money' from the home fans followed the final whistle.