System and method for enabling graphical program polymorphism. A "polymorphic node" to be included in a graphical program may be created and configured. A parameter interface that defines allowable inputs and outputs for the polymorphic node may be specified, and a set of functions or subprograms may be associated with the polymorphic node. The functions may have parameter interfaces that specify particular data types for the inputs/outputs of the functions. Once a polymorphic node is included in a graphical program, the node may be configured with typed inputs and outputs. The graphical programming system may determine a particular function associated with the polymorphic node to match the polymorphic node to, based on the data types of the configured inputs and outputs. This determination may also be based on an ordering specified for the set of functions associated with the polymorphic node. A best-fit heuristic for automatically making this determination is described. The user may also manually specify which function to match the polymorphic node to. The graphical program may be generated just as if the matched function were called directly, thus incurring no execution performance loss.