Dutch-based oil trading group Trafigura is to pay the Ivorian government $198m (£102m) for a clean-up and inquiry after a"toxic waste" incident in 2006.
Residents suffered headaches, vomiting and breathing difficulties
Trafigura say this is not "damages" and that there is no admission of liability on their part for whatever happened.
Ten people died and many fell ill after waste was shipped to Abidjan and left around the city in August.
As part of the deal, the Ivory Coast will drop any prosecutions or claims, now or in the future, against the firm.
Trafigura also said its employees Claude Dauphin, Jean-Pierre Valentini and Nzi Kablan, held by the Ivory Coast authorities after the incident, would now be released.
Thousands suffered diarrhoea, vomiting, breathing problems and nosebleeds and 10 died, say Ivorian health officials.
After announcing the clean-up settlement Eric de Turckheim, a Trafigura director, said: "Both the Ivorian government and Trafigura can now move forward together to act in the best interests of the people of Abidjan."
He said Trafigura would continue doing business in the Ivory Coast.
Trafigura first attempted to discharge the chemical slops from one of its tankers, the Probo Koala, in the Dutch port of Amsterdam in early August.
But the company that was to dispose of the waste suddenly increased its charges dramatically - asking for more to treat the waste. Trafigura refused, and the tanker proceeded to Nigeria.
There it failed to reach an agreement with two local firms about offloading the waste and only in Ivory Coast did it find a company to handle the waste.
On 19 August the waste was discharged near Abidjan, the commercial capital. Two weeks later the first complaints arose. Instead of being incinerated as it should have been, the waste had been dumped.
Trafigura said it had been given to a local accredited company in Abidjan's main port to deal with properly.