Four sediment cores were collected in Suruí Mangrove. Cores 0.30-m long were sliced into small cores corresponding to 0–0.03, 0.05–0.10, 0.10–0.15, 0.15–0.20, 0.20–0.25, and 0.25–0.30-m depths. Polycyclic aromatic hydrocarbons, total organic carbon (TOC), and total sulfur (TS) were determined. Total organic carbon varied between 0.8% and 7.8%, with mean values varying according to sampling location (5.2% for core 1, 3.2% for core 2, 4.2% for core 3, and 2.7% for core 4). Total sulfur also varied in the studied cores with a mean ± standard deviation of 1.1% ± 0.7%. The lowest value (0.01%) was found in core 2 (0.10–0.15 m), and the largest one (2.6%) was observed in core 4 (0.25–030 m). The TOC/TS ratio indicated that most sediments showed reducing characteristics, except for four samples (core 1 of 0.10–0.15 m and 0.25–0.30 m, and core 2 of 0–0.03 m and 0.05–0.10 m). Total PAH concentrations varied between 4.4 and 1387 µg g⁻¹, indicating a local and restricted contamination of parts of the studied area. The highest percentages for total and carcinogenic PAHs and toxic equivalent factors were found in the sediment from core 1 from Suruí Mangrove, with a predominance of benzo[k]fluoranthene, benzo[a]pyrene, and naphthalene. In cores 3 and 4, collected closer to Guanabara Bay, benzo[a]anthracene and benzo[a]pyrene were also found. The sediment in Suruí Mangrove is functioning as a reservoir of compounds that are carcinogenic to the fauna and flora of the mangrove itself, and to the adjacent waters of Guanabara Bay.