Swiss chard (Beta vulgaris L. subsp. vulgaris) is a nutritionally rich leafy vegetable of moderate economic value. Despite being the first species among the genus Beta to be cultivated, knowledge regarding its biodiversity and agronomic and morphological properties is limited. The objective of this study was to evaluate the agromorphological characteristics of the Turkish Swiss chard genetic resources, and to determine their genetic relationships and diversity. To achieve this, a total of 52 Swiss chard accessions from a wide range of environmental and geographical origins in Turkey and two cultivars (one local and one foreign) were investigated. Fourteen qualitative and 13 quantitative agromorphological traits of these accessions were analyzed over the two consecutive growing seasons. Principal component analyses (PCA) explained 77.26% of the total variations for the agromorphological traits, while the hierarchical agglomerative clustering methods separated the accessions into four clusters and leaf weight, petiole width, petiole thickness, lamina length, and lamina width were the primary characteristics to distinguish the Swiss chard accessions. An extremely high degree of agromorphological diversity was observed in the Turkish Swiss chard genetic resources, and promising germplasm was identified to improve the cultivars for yield and leaf traits.