Mexico held on to clinch a 50-42 win over France at North Greenwich Arena.
In what was effectively a two-way play-off, the Mexicans held a 13-point cushion in the fourth quarter but then came under immense pressure from the French, who came up short to finish with a 0-4 record.
The loss means France will now meet the fifth-placed team in Group A in a classification match for 9th place on Tuesday.
The Mexicans will finish fourth in their pool, regardless of the result of their game on Monday against group winners Germany, but they achieved their immediate priority of progressing into the knockout stages.
Led by a team-high 18 points from Lucia Vazquez Delgadillo, Mexico's 46 per cent shooting in the first half was enough to overturn an early 6-2 French lead. They moved in front for good when Anaisa Perez Pacheco scored inside with 1:23 left in the opening quarter.
It sparked a 10-2 Mexican run that propelled them towards a 26-20 half-time advantage.
And seven unanswered points in the third period widened the gap, which peaked at 39-26 when Vazquez Delgadillo hit the initial basket of the fourth.
But the French fought back, led by their captain Angelique Quemener-Pichon, who ended with a game-best 22 points.
A 10-1 burst reduced their deficit to just 42-40 with 4:27 to go, but Mexico delivered a decisive late response.
Meanwhile, in the men's competition, another triple-double from Patrick Anderson led Canada to a hard-fought 73-66 win over Germany that sends them clear at the top of Group B with a 4-0 record.
Anderson, who had what Canadian team officials said was his first career international triple-double against Britain two days ago, collected 25 points, 15 rebounds and 12 assists to power Canada, with captain Bo Hedges adding 24 points.
The 33-year-old Anderson retired after Beijing 2008, but returned to action last year with the goal of playing in a fourth career Paralympic Games, and he is more than making the hard work pay off so far.
Dirk Passiwan had 29 points for Germany.
Japan are still in with a chance in the group after beating Colombia 63-49, eliminating the South Americans, who will now play in Wednesday morning's classification game for 11th place.
Reo Fujimoto had 21 of his 27 points in the first half, and added 14 rebounds for Japan.
Colombia began with a 10-3 start, but had little to shout about thereafter.