Fruit flies (Diptera: Tephritidae) are the primary pests of horticultural crops worldwide, causing both direct and indirect damage to the fruit production, including Anastrepha grandis (Macquart, 1846), which exclusively infests Cucurbitaceae fruit. Dose-response tests were used to examine the effects of gamma radiation exposure on 24 – 48 h old eggs and third instar larvae, both in vitro and in Atlas squashes (Cucurbita moschata). The following physicochemical properties of Atlas squashes exposed to gamma radiation were evaluated: titratable total acidity, sugar, pH, external colouration, and texture. It was found that under in vitro conditions, a 20.0 Gy dose of gamma radiation was able to prevent larval eclosion, but a 200 Gy dose was necessary to prevent emergence after the exposure of third instar larvae. In Atlas squashes, 200 and 250 Gy doses of gamma radiation were able to prevent the emergence of A. grandis adults from eggs and larvae, respectively. The radiation doses estimated by Probit 9 to prevent emergence from squashes infested with eggs and third instar larvae were 257.13 Gy and 270.25 Gy respectively. The use of gamma radiation did not significantly affect the physicochemical properties of Atlas squashes, which suggested that gamma radiation may represent a potentially useful technique for the quarantine control of A. grandis in cucurbits.