The cucumber (Cucumis sativus L.) is an economically important vegetable crop cultivated worldwide, including Vietnam. This study aims to determine the physiological ripening time of cucumber fruit to establish a scientific basis for optimizing fruit quality, harvest, and preservation. Changes in the physiological and biochemical parameters during the growth and development of cucumbers from 2 to 12 days after anthesis (DAA) were observed and analyzed. The fruit reached its maximum size in length, diameter, volume, and weight at 11 DAA. The chlorophyll content of the fruit reached its maximum value at 8 DAA and then decreased. The carotenoid content was low during fruit formation and increased until fruit ripening. The vitamin C content and reduced sugar content increased continuously and reached a maximum of 11 DAA before decreasing slightly. The starch content, total organic acid content, and tannin content reached a maximum of 9 DAA and then gradually decreased. The pectin content increased from fruit formation until fruit ripening. Our results indicate that cucumbers should be harvested at 11DAA to maximize the nutritional value of the fruit for consumption and processing.