Toyota will continue their engine deal with Jordan when the team is re-branded as Midland F1 next season.
Jordan have amassed just 11 points in the constructors' championship
The Japanese manufacturer, which also runs its own team, will provide Midland with the latest specification of their new V8 engine for one year only.
The deal rules out any possibility of Williams using Toyota engines in 2006.
Williams are expected to team up with Cosworth next season rather than continue their partnership with BMW, who have bought out Sauber.
Toyota has supplied Jordan since the start of this season but the team has struggled for money after being taken over by Russian businessman Alex Shnaider, who is focusing his main financial input on 2006.
The new deal could allow Toyota to use Jordan as an extra test bed for their new engine following rule changes that see engine designs switch from the
current 3-litre V10 to a 2.5-litre V8 next year.
Jordan team boss Colin Kolles said: "The co-operation with Toyota has been a key element for Jordan this season and with their commitment to our team they have put Formula One above their own exclusivity.
"We are in a transition year and the exceptional Toyota engine reliability record is essential for us to gather data to be used to develop the 2006 car. I also hope we can help Toyota in the battle for world championship honours."