Is there a cap on legal costs that can be awarded in a family court case?

There isn't a single fixed dollar cap on costs in Ontario family court cases generally — costs awards are discretionary and assessed based on the specific circumstances, including the complexity of the issues, the conduct of the parties, and the reasonableness of the fees actually incurred, rather than a flat maximum set by legislation. A judge deciding costs will look at what's proportionate and reasonable for the specific step or the case as a whole, which can result in very different costs awards between a straightforward, cooperative case and a lengthy, contentious one.

What does act as a practical constraint is that costs awarded are generally tied to a reasonable proportion of the actual fees incurred, assessed against the applicable costs scale, rather than an amount unrelated to the real cost of the litigation — so a party can't recover costs wildly out of proportion to what the case actually involved. Because there's no simple cap to point to, and because costs outcomes vary so much based on conduct and complexity, anyone concerned about costs exposure should discuss their specific situation with a lawyer rather than relying on a general rule of thumb.