The sweet cassava root age and pre-harvest managements can modulate the oxidative metabolism and provide a longer shelf life. Moreover, the evaluation of enzymes envolved in oxidative protection regarding the phenolic metabolism can be an additional approach to understand how the cultivation affects the post-harvest physiological deterioration tolerance in sweet cassava roots. Thus, the aim of this study was to evaluate the oxidative enzymatic protection associated to oxidation mediate by PPO and POD, in response to population density and harvest time of sweet cassava roots, cv. "Mossoró". The roots were cultivated in field conditions in the Brazilian Semiarid, under irrigation. The experimental design was a randomized complete block with three replications. Treatments corresponded to four harvest times (240, 300, 360, 420 days after planting -DAP) and four population densities (10,000, 12,500, 15,000 and 17,500 plants ha -1 ). Sweet cassava roots were sampled and the total soluble phenol content as well as soluble protein content were measured. Also, polyphenol oxidase (PPO), peroxidase (POD), superoxide dismutase (SOD), catalase (CAT) activity was evaluated. The roots showed higher total soluble phenol content at 300 and 360 DAP and higher protein content at 240, 300 and 360 DAP, for all densities avaluated. Planting densities extremes, of 10,000 and 17,500 plants ha -1 , resulted in higher levels of phenolics compounds and SOD activity. However, did not promote difference in the levels of soluble proteins. There was a significant reduction at PPO, SOD and CAT activity with late harvest, which did not occur for POD activity. Therefore, younger roots have higher oxidative enzymatic protection when compared to older roots in Semiarid conditions.