The cucumber (Cucumis sativus L.) contains a significant amount of antioxidants, especially when harvested at the right time. The present study evaluated differences in nutrients, total phenolic content, and antioxidant activity of cucumbers grown in Kundasang, Malaysia, at the semi-ripe fruit (SR) and ripe fruit (R) maturation stages. Independent T-tests revealed significant differences (p < 0.05) between proximate analysis data for the SR and R stages. Moisture content at the SR stage (98.217 ± 0.068%) was higher than for R (97.617 ± 0.221%); similar differences were observed for the carbohydrate content (