Abstract: Background: Recently, there is increasing demand for consumption of natural and healthy foods. Fruits (and watermelon among them) are believed to contain variety of dietary phytochemicals that may have beneficial effect on human health. Objective: The aim of this study was to prepare three samples from watermelon fruit (of Saudi origin ) and to determine proximate composition, mineral, vitamin, flavonoids and beta sitosterol contents of the three samples. Methodology: Three samples were prepared from interior pulp region, exterior pulp region and from the rind of watermelon fruit. Proximate composition was determined by conventional official methods, analytical determination of minerals was performed by ICP-MS (inductively coupled plasma-mass spectrophotometer), vitamins and flavonoids were determined by High Performance Liquid Chromatography (HPLC) and β-sitosterol by Gas Chromatography (GC) techniques. Statistical analysis was performed by using SPSS software. Results: Moisture (ranged from 85-95%) was the predominant component in the samples. Carbohydrates ranged from 62.00-87.14% in dry weight basis, while fat content was low in the three watermelon samples. Potassium was the predominant mineral and ranged from 100.50-489.24 mg/100 g, vitamin C ranged between 2.50-8.30 mg/100 g, vitamin B6 0.060-0.150 mg/100 g and vitamin E 0.01-0.04 mg/100 g in the three watermelon samples. β-carotene concentration was high in the interior pulp (0.610 mg/100 g) compared to that in the rind (0.120 mg/100 g). Rutin was the only flavonoid detected in watermelon fruit, rutin concentration in the interior pulp sample was 1.66 mg/100 g. β-sitosterol is a phytosterol found in all parts of watermelon fruit, ranging from 0.140-0.627 mg/100 g. Conclusion: The results of this study may highlight the potential of watermelon fruit as a source of nutrients and anti-oxidants that may be considered for human nutrition and health.