Background: With increasing concern over food insecurity, there is the need to incorporate wild edible plants in our meals as they can provide adequate level of nutrition when consumed as food. Aim: The objective of this study was to evaluate the proximate composition, elemental composition, total phenolic content, total flavonoid content and gas chromatography–mass spectrometry (GC-MS) profile of Lantana trifolia. Setting: This study was carried out in Juja, Kenya where the samples were collected, prepared and stored at the Department of Chemistry, Jomo Kenyatta University of Agriculture and Technology. Methods: The proximate and elemental compositions of the leaves, stalk and root samples were evaluated by using standard procedures, whilst the total phenolic and flavonoid contents were evaluated by using Folin–Ciocalteu and aluminium chloride method. The secondary metabolites present in the crude methanolic extracts of the whole plant were determined by using GC-MS. Results: The proximate and elemental analyses of the plant revealed that L. trifolia can be a good source of essential elements, proteins, crude fibre and carbohydrates. The protein, fat, crude fibre and carbohydrate contents in the leaves were found to be higher compared with the stalks and roots, whilst the ash and moisture contents were found to be higher in the roots. The concentrations of calcium, iron, magnesium and zinc in the leaves were found to be 8860.75 ± 565.27, 11 003.10 ± 143.24, 1520.25 ± 26.85 and 39.66 ± 15.68 mg/kg, respectively, compared with the roots and stalks, which were lower. Conclusion: The concentration of total phenolic and total flavonoid compounds and GC-MS profile of the methanolic extracts revealed that L. trifolia can be a good source of secondary metabolites, some of which have reported to be free radical scavengers. Hence, L. trifolia can not only be used as a source of important secondary metabolites, but its nutritional content suggests that the plant can be used to combat nutrient deficiency amongst many communities who lack adequate resources, because it thrives in the wild.