The in vitro anti-sickling and free radical scavenging properties of leaf extracts of Moringa oleifera were investigated. In the present study, amino acid profile, vitamin C concentration, the phytochemicals and proximate compositions of M. oleifera leaf were also determined. Anti-sickling effect of aqueous and ethanol extracts of M. oleifera were assessed by incubating the extracts with HbSS blood samples and inducing sickling in vitro using 2% Sodium metabisulfite (Na2S2O5). Effect of extract on Fe2+/Fe3+ was also determined. Free radical scavenging properties of M. oleifera was assessed by determining the reducing power of nitric oxide radical and the hydroxyl radical scavenging effects using standard methods. Results obtained revealed the presence of important phytochemicals in M. oleifera leaf. Results also showed that M. oleifera leaf contain substantial quantities of essential amino acids, some of which include Histidine 4.33 ± 0.22, Phenylalanine 4.78 ± 0.24, Valine 9.77 ± 0.49, Leucine 3.56 ± 0.18 (in g/100g extract). Results also showed that M. oleifera leaf is a rich source of carbohydrate (47.55 ± 2.38%), protein (15.22 ± 0.76%), lipid (13.82 ± 0.69%), fibre (9.02 ± 0.45%), moisture (7.28 ± 0.36%), ash (7.11 ± 0.36%). Polymerization inhibition results obtained with M. oleifera leaf extracts showed that the extract was significantly effective at inhibiting polymerization of HbSS hemoglobin, with the ethanol extract being more potent. M. oleifera leaf extract inhibited nitric oxide radicals, achieving 30% inhibition at 1000µg/ml, and effectively scavenged 80% hydroxyl radicals at 1000µg/ml. M. oleifera extract was equally effective in the reduction of Fe3+ to Fe2+, with the aqueous extract having a higher reducing power than the ethanol extract. Therefore, the medicinal plant M. oleifera has proven to be nutritionally and therapeutically beneficial and thus may be further researched and developed for the effective management of sickle cell disease (SCD) and its related syndromes.