The first alarm was raised a few weeks before the finals, when tests conducted on the Seine revealed a concentration of E. Coli bacteria that quadrupled the levels permitted by the International Triathlon Union. The results varied over successive days, but the rain that fell in the French capital—a factor that causes faecal waste to end up in the river—forced the organisers to cancel the training sessions scheduled for the 28 and 29 July, just a couple of days before the official start.

The situation, far from improving after that weekend's rainfall, also caused the postponement of the first final, the men's race, which was initially set to take place on the 30th. The poor water quality at that time could have jeopardised the health of the athletes, leading to the decision to delay the event.

With this background, the starting gun was finally fired on the 31st with the women's final, a category that did keep to the scheduled date. French athlete Cassandre Beaugrand achieved every sportsman's dream by winning the gold medal in the triathlon in her home country, amidst the fervour of the crowd and the tricolour flags that accompanied her as she crossed the finish line alone.

Beaugrand, 27 years old and a resident of Loughborough, Great Britain, secured victory after making her move two kilometres from the finish in the final running segment, where she dashed the hopes of Switzerland's Julie Derron and the British world champion Beth Potter, who took silver and bronze respectively. Beaugrand, who hails from Livry-Gargan, was no stranger to this type of competition as she was competing in her third consecutive Olympic Games and had already stood on the podium with a bronze in the mixed relay at Tokyo 2020.

However, the bacteria once again became the discordant note. After completing the swimming segment in the Seine, Belgian triathlete Claire Michel fell ill for several days with vomiting and diarrhoea until she had to be hospitalised due to an E. Coli infection. This ruined her team's chances, as they were unable to compete in the mixed relay final due to her absence. While the Mayor of Paris, Anne Hidalgo, was quick to claim there was no connection between the illness and the river swim, the Belgian Olympic Committee (COIB) and the country's triathlon federation "hope lessons will be learned for future competitions."

The weather continued to cooperate throughout the day, allowing the schedule to be completed with the men's triathlon final. Britain's Alex Yee (Lewisham, 26 years old) restored his country's dominance in this sport, emulating his compatriot and double Olympic champion Alistair Brownlee, with a gold medal forged in an epic race, culminating in a historic final comeback that dashed the hopes of New Zealand’s Hayden Wilde, who took silver in Paris 2024. With this title, Great Britain leads the all-time medal table in this category with their third gold.

Yee's victory was magical, having won silver at Tokyo 2020. The Briton, inspired to become a triathlete by the successes of the Brownlee brothers, overtook Wilde, who had led the race, just 400 metres from the finish line at the Pont Alexandre III. Yee capitalised on the New Zealander's final fade to embrace Olympic glory and renew the titles won by his idol Brownlee in London 2012 and Rio 2016, the only one with two Olympic crowns. The bronze medal went to France's Leo Bergere, the current World Championship leader. Another medal for France after Beaugrand's gold in the women's event.

Amidst this ongoing uncertainty regarding the weather and water quality, 5 August finally arrived, the day of the mixed triathlon event, whose prior training sessions also had to be cancelled due to a new threat from the Seine. In this case, a final sprint by Laura Lindemann secured gold for Germany in the final. The United States and Great Britain took the silver and bronze medals respectively, after France, the strong favourite, saw its hopes dashed following a fall in the cycling segment.

The German team, composed of Tim Hellwig, Lisa Tertsch, Lasse Lührs, and Lindemann, clinched the title thanks to an outstanding performance by their final runner in the 1,800-metre run that decided the podium. The winning team crossed the finish line with a total time of 1:25:39, allowing them to edge out their closest rivals by just one second. This was the second time that the mixed relay triathlon featured in the Olympics, following its debut at Tokyo 2020.