We present a complex field formulation of the quantum Fisher estimation theory that works natively with complex statistics on the dependence of complex parameters. This states new complex versions of the main quantities and results of the estimation theory depending on complex parameters, such as Fisher information matrices and Cramér-Rao bounds. This can be useful in contexts where the quantum states are described through complex parameters, as coherent states or squeezed states. We show an application of our theory in quantum communication with coherent states.