Background and Objective: Blood loss represents a long-standing concern of radical prostatectomy (RP). This study aimed to assess how red line cell values changed following robot-assisted radical prostatectomy (RARP) for prostate cancer (PCa). Materials and Methods: The blood panels of 453 consecutive PCa patients undergoing RARP at a single tertiary academic referral center, from September 2020 to April 2022, were reviewed. Data from 363 patients with the blood panel available for the following timeframe: within seven days before surgery, six hours after surgery, and the first three postoperative days, were analyzed. Specifically, hemoglobin (Hb, g/dL), red blood cells (RBCs, ×106/μL), and hematocrit (HCT, %) trends were collected. Results: Considering the Hb trend, the median values in the preoperative day, postoperative day (POD) 2, and POD 3 are 14.7 (interquartile range (IQR) = 13.9–15.4), 12.1 (IQR = 11.2–12.9), and 12.2 (IQR = 11.2–13.1), respectively. The ∆ between preoperative day and POD 2 is 2.5 (IQR = 1.8–3.2) (p < 0.001). Considering the RBCs trend, the median values in the preoperative day, POD 2, and POD 3 are 4.9 (IQR = 4.7–5.3), 4.1 (IQR = 3.8–4.4), and 4.1 (IQR = 3.8–4.5), respectively. The ∆ between preoperative day and POD 2 is 0.9 (IQR = 0.6–1.1) (p < 0.001). Considering the HCT trend, the median values in the preoperative day, POD 2, and POD 3 are 44.4 (IQR = 41.7–46.6), 36.4 (IQR = 33.8–38.9), and 36.1 (IQR = 33.5–38.7), respectively. The ∆ between preoperative day and POD 2 is 7.8 (IQR = 5.2–10.5) (p < 0.001). Conclusions: Overall, patients undergoing RARP experience a significant, but clinically limited, decline in red line cell values between the preoperative time and the second day post-surgery. These observations are important to provide physicians with knowledge of the expected postoperative course and, thus, to improve the quality of patient care.