A tight affair was settled in the 79th minute at the Tottenham Hotspur Stadium, with Son receiving Japhet Tanganga's square pass in the box before firing past Bernd Leno.
Three wins and two draws from their five pre-season games means Nuno Espirito Santo's side head into the Premier League campaign, which begins against reigning champions Manchester City on August 15, unbeaten.
Despite Spurs' victory here moving them level on points with Chelsea, the Blues win the mini-tournament having scored the greater number of goals in their two matches.
Chances were few and far between for the most part. Leno denied Son from point-blank range, while Alexandre Lacazette hit the post from the edge of the box.
Though it was technically a friendly, the competitive nature of the fixture was evident with a crunching Dele Alli tackle on Nicolas Pepe earning a yellow card.
👤 @Ben6White— Arsenal (@Arsenal) August 8, 2021
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Despite the result, the boss was full of praise for our new signing... 👇
Alli twice went close to breaking the deadlock; the England international hitting the post either side of half-time.
The game appeared to be heading for a stalemate but Son – a scorer in two of the three most recent competitive encounters between the sides – snatched the victory for Spurs 11 minutes from time with his third goal of pre-season.
Mikel Arteta's Arsenal, which launches its Premier League season away at Brentford on 14 August (AEST), had a chance to equalise late on, but Pierluigi Gollini denied Bukayo Saka from close range.