Mexico has a wealth of plant genetic resources, including Capsicum species. In southern Mexico, specifically in the western part of the Yucatan Peninsula, Maya farmers have preserved a great diversity of chilli pepper landraces of C. annuum, C. frutescens and C. chinense. However, the morphological diversity, capsaicinoid content, conservation status and potential use of these species have not been studied. To fill this gap and generate information to support the conservation and use of these species, we characterized the phenotypic diversity and capsaicinoid content for nine chilli pepper landraces from the western Yucatan Peninsula by assessing 15 quantitative and 39 qualitative traits for 10 plants of each landrace. For quantitative variables, two groups of chilli pepper landraces were obtained by principal component analysis and cluster analysis. Group I was formed by Rosita, Bobo, Dulce, Xcat'ik1, Xcat'ik2 and Verde landraces; Group II included the Maax, Bolita and Pico Paloma landraces. For qualitative variables, three groups of chilli pepper landraces were obtained; Group I included Dulce, Bobo, Xcat'ik1, Xcat'ik2 and Verde landraces, Group II only included the Rosita landrace, and Group III included Maax, Bolita and Pico Paloma landraces. Ultra-performance liquid chromatography–photodiode array (UPLC-PDA) quantification of capsaicinoids indicated higher values in landraces Rosita (14,062.3 μg/g D.W), Bolita (5928.1 μg/g D.W), Maax (3438.4 μg/g D.W) and Pico Paloma (3138.9 μg/g D.W). The Yucatan chilli pepper landraces provide valuable diverse germplasm for morphological characteristics and capsaicinoid content that can be used in breeding and conservation programmes.