An efficiently-transformed digital self-interference canceller, preferably including an FD transformer, a TD transformer, a channel estimator, a composer, and a controller. The canceller can optionally include a channel memory, a predictor, and/or an extender. A method for digital self-interference cancelation, preferably including receiving inputs, transforming the inputs, generating outputs based on the transformed inputs, transforming the outputs, and/or generating a cancellation signal based on the outputs.