We assessed the health status and hematologic and blood chemistry values of 48 juvenile green turtles ( Chelonia mydas) on the southeastern coast of Brazil (25°S 48°W). We investigated the impact of size and weight, nutritional condition, and presence of epibionts and fibropapilloma tumors. Nutritional status was good for 39 animals; these animals had higher serum albumin, cholesterol, and phosphorus concentrations than 9 animals with a fair nutritional score. Reference values for hematology and biochemistry were calculated for 39 individuals without fibropapillomas (FPs). Turtles with epibionts ( n = 33) had lower hemoglobin (Hb) than turtles without epibionts ( n = 15; t = −2.09, p = 0.04), and the area occupied by epibionts was positively correlated with the white blood cell count ( r = 0.37, p = 0.03). FP turtles had significantly lower hematocrit (Hct), Hb, and red blood cell (RBC) counts than non-FP turtles; serum albumin and cholesterol were higher in non-FP than FP turtles. A negative correlation between curved carapace length (CCL) and Hct ( r = −0.51, p = 0.0002) and RBC ( r = −0.47, p = 0.0007), and between serum cholesterol, sodium, and uric acid and CCL ( r = −0.53, p = 0.0001; r = −0.38, p = 0.007; r = −0.35, p = 0.014, respectively) were identified. The health of turtles appears to deteriorate as they get larger, which manifests in more FPs, decreased body condition, and systemic physiologic changes consistent with chronic disease including lower Hct, RBC counts, serum cholesterol, sodium, and uric acid.