The present investigation on “Antioxidant and phytochemical characterizations of custard apple (Annona squamosa L.)” was conducted at Department of Biochemistry, Junagadh Agricultural University, Junagadh with objectives i) to examine fruit quality of different custard apple genotypes, ii) to measure antioxidant and antidiabeitic activity from leaf extact of custard apple genotypes and iii) to assay phytochemicals and phenolics compounds from leaf methanolic extact of custard apple. Among 30 custard apple genotypes, K-2, Aml-8, Aml-7, Aml-8 and N-1 showed highest weight, volume, girth, length and pulp to seed ratio respectively. Fruit quality checked by different biochemical testes. Total soluble solids found highest in Aml-2 (25.74 %brix) which was at par with B-2 (25.73), Aml-1 (25.48), B3 (25.37), Lok-1 (25.37). However, total carbohydrate measured highest (14.41%) in Lok-1, Lok-2, Aml-4, Aml-7, Aml-9, Aml-10. The highest (2.05 mg%) free amino acid was recorded in Sindham. However, the maximum (13.03 %) dietary fiber recorded in B-1 genotype. The highest value (4.39%) of ascorbic acid was found in Aml-8 genotype of custard apple. The highest carotenoids (0.88 mg.g-1) were observed in Aml-12 genotypes followed by M-1 (0.64 mg.g-1) genotype of custard apple. The free radical scavenging activity as percent DPPH inhibition was examined highest in S-3 (31.10 %) genotype of custard apple, while antidiabetic activity as percent inhibition of α-amylase activity were recorded maximum (43.64%) in K-2 genotype of custard apple. Fractions of phenolics i.e. alkaloids, glycosides and flavonoids, and anthocyanins are found in better amount in K-2, Lok-1, K-1, Aml-2, Aml-6, Aml-7 and N-1 genotypes to exhibit antioxidant and antidiabetic activities. Among the individual phenolics, salicylic acid was found only in K-2 which exhibited maximum antidiabetic activity. Ferulic acid examined in S-3 for antioxidant activity. Key words: Custard apple, DPPH, Food quality, Antidiabetic, Phytochemicals, HPLC.