There is provided mechanisms for selecting beam direction for a radio communications device. A method is performed by the radio communications device. The method comprises obtaining radio channel estimates of a radio channel on which radio waves have been transmitted between the radio communications device and another radio communications device at an angle of arrival and departure. The method comprises determining a Doppler shift from the radio channel estimates. The method comprises estimating at least one of the angle of arrival and departure of the radio waves based on the Doppler shift. The method comprises selecting a beam direction for a signal to be transmitted between the radio communications device and this another radio communications device over the radio channel according to the estimated angle of arrival or departure.