The Guadalupe Bass, Micropterus treculii is endemic to the Hill Country region of central Texas, US, and its entire native distribution is within Texas, including portions of the Brazos, Colorado, Guadalupe, and San Antonio River basins. Currently, the genetic integrity of Guadalupe Bass populations are threatened by hybridization with introduced, nonnative Smallmouth Bass, M. dolomieu. Species-isolating mechanisms (or lack thereof) are not well understood for these two species. To identify potential mechanisms influencing hybridization in Guadalupe Bass populations, our objectives were to characterize: (1) spawning season and duration, (2) nesting habitat, (3) courtship behaviors (including color pattern changes), and (4) parental care pattern. The reproductive ecology (spawning season, nest sites) and behavior (courtship, parental care) of Guadalupe Bass were found to be similar to what has been reported in Smallmouth Bass, possibly contributing to continued potential for hybridization. Guadalupe and Smallmouth Bass share 12 reproductive behaviors and similar color patterns during courting and spawning interactions. This study is the first to report an individual male Guadalupe Bass simultaneously courting and spawning with two to four females in one nest, suggesting the need for further investigation of links between hybridization potential, sex ratio and population structure in Guadalupe Bass. We recommend investigation of female mate choice and sexual competition comparing Guadalupe Bass and Smallmouth Bass. Additionally, future conservation efforts should focus on nesting habitat in existing pure strain Guadalupe Bass populations.