This paper presents a rigorous analysis to determine the noise parameters of linear noisy microwave networks with any number of ports. The analysis expands a well-established approach for the determination of the noise parameters of a linear two-port network to any linear $N$ -port networks and enhances the understanding of its measurement procedure as a particular case of this analysis. A thorough discussion of the results of this analysis identifies constraints and highlights practical requirements for a successful noise characterization setup of any $N$ -port networks. The analysis is then applied to the measurement of four-port networks. The determination of passive network’s noise parameters allows the experimental validation of the theory, while the determination of an active four-port network’s noise parameters is of particular interest, because its differential noise figure can be determined directly from its noise parameters without the use of external baluns.