Introduction: Human identification, an aspect of forensic anthropology, is the recognition of an individual based on the physical characteristics unique to the individual. Among the four main attributes of biological identity, sex determination is usually the first step in the human identification process. The objective of this study was to assess the dimorphic status of mesio-distal and bucco-lingual widths of maxillary first permanent molars of the Urhobos in South-Southern Nigeria. Material and methods: The study subjects were 100 male and 100 female Urhobos, aged 17-26 years. The descriptive study adopted the purposive sampling technique. Intra-oral measurements of mesio-distal and bucco-lingual dimensions of the first maxillary molars were taken using digital vernier caliper after informed consent was obtained. The data obtained were subjected to statistical analysis using descriptive statistics and t-test to compare dimensions between males and females. P-value ≤ 0.05 was considered statistically significant. Results: The mean mesio-distal width was 9.69 mm (right) and 9.62 mm (left) in males; 9.40 mm (right) and 9.56 mm (left) in females. The mean bucco-lingual width was 10.45 mm (right) and 10.49 mm (left) in males and 10.21 mm (right) and 10.23 mm (left) in females. The differences between males and females in all dimensions measured except left maxillary mesio‑distal width were statistically significant (P-value < 0.05). All the dimensions exhibited sexual dimorphism of 3.0% except left maxillary mesio-distal width which showed 1.0%. Conclusion: The mesio-distal and bucco-lingual dimensions of the maxillary first molars may be used as an aid in sex discrimination.