Sequence-related amplified polymorphism (SRAP) markers were used to evaluate the intra- and interspecific variation among 40 Lathyrus genotypes (four species) (Fabaceae). Ten SRAP primer combinations resulted in a total of 94 bands, and they exhibited high interspecific variability. The genetic differentiation among Lathyrus, estimated using AMOVA, was highly significant. The results indicated that 58% of the total genetic variation existed among species, and 42% of the differentiation was within species. This was explained by the high level of genome conservation of these species as well as the recent and slow evolution of this genus. These results were confirmed by the topology of the neighbor-joining cladogram and the results of the principal coordinate analysis. Our data support previous results based on seed protein diversity. These results make SRAP markers choice markers for the study of functional polymorphism that is directly related to the transcriptomic data. The SRAP markers used in this study provide an accurate picture of the population structure within Lathyrus germplasm, which is critically important information for the design of genetic diversity and structure analyses. Moreover, further extensive studies are necessary to fully examine other Lathyrus species and tests that adopt the SRAP technique to enrich the Lathyrus library for next-generation sequencing, thus providing a potent protocol for the study of polymorphism.