A modular computer system is provided. In one embodiment, the system includes a computer server having a first printed circuit assembly disposed within a first housing and an expansion connector. The computer server is configured to be coupled to a modular expansion unit via the expansion connector to convert the computer server from a base configuration to an expanded configuration. In various embodiments, the expanded configuration may provide additional processing power, additional memory, or the like. A method of assembling a modular computer system is also provided.