Yes, you can mutate props. But no, it's probably not going to do what you want if you did it intentionally. If react added Object.freeze() (or deepFreeze) to the component render invoker, everything would be the same, except props would be formally immutable, instead of being only expected to be immutable. But this seems like a distinction without much of a difference, because if you just try to use a pattern like that without having a pretty deep understanding of react internals, it's not going to do what you wanted anyway.