Introduction: Horned melon (Cucumis metuliferus E. Mey. ex Naudin) remains an underutilized crop in Zimbabwe, despite its significant potential to bolster food and nutritional security in challenging environments due to its adaptive nature.

Methods: This study, conducted over two growing seasons (2024–2025) at Midlands State University, characterized the agro-morphological diversity of 24 landrace accessions collected from Mashonaland East using a Randomized Complete Block Design (RCBD).

Results: The research revealed substantial phenotypic variation (p < 0.001) across all measured traits. Certain accessions, notably Acc5, Acc8, Acc2, and Acc20, demonstrated superior agronomic performance, with Acc5 emerging as a particularly promising candidate for high-yield variety development or hybridization. Furthermore, Acc1 exhibited early maturity, a critical characteristic for developing climate-resilient cropping systems, while Acc24's thornless phenotype offers distinct advantages for handling and marketability. Yield displayed strong positive correlations with vine length (r = 0.58**), individual fruit weight (r = 0.59**), and the total number of fruits (r = 0.76**), underscoring these traits as primary determinants of productivity. A nearly perfect correlation (r = 0.99**) between the timing of male and female flowering indicated a tightly synchronized reproductive phase, which is essential for optimizing yield. Conversely, traits related to germination and seeds showed minimal impact on overall yield. A linear model (R² = 0.93) further confirmed that vine length, fruit weight, and fruit count significantly drive yield, while the number of thorns negatively influence it.

Conclusion: Yield is primarily influenced by vegetative vigor and reproductive efficiency. Breeding germplasm, such as high-yielding accessions (Acc5 and Acc8), an early-maturing line (Acc1), and a thornless variety (Acc24), emphasize the need to focus future breeding efforts on enhancing vegetative and reproductive characteristics.