In the tribe Andropogoneae, morphological variation is remarkable, mainly in the inflorescence on the pair of spikelets which are the core elements of the inflorescence. The genus Andropogon includes the Andropogon lateralis complex, which is distributed primarily in South and Central America, comprising approximately twelve taxa and inter-specific hybrids. The aim of this study was to assess morphological variation in the A. lateralis complex through morphometric analyses of specimens from natural populations. For this purpose, univariate ANOVA, as well as principal component analysis and discriminant analysis of 19 morphological variables of synflorescences were performed, revealing differences between species and interspecific hybrids. The selected diagnostic traits of species and hybrids based on quantitative characters of the synflorescences provided a valuable tool for taxonomic studies in the genus. The results obtained made it possible to generate the first identification key that includes both species and hybrids of the A. lateralis complex for South America.