Introduction: The Opossum is a marsupial related wild life species belonging to the order Didelphimorphia. They inhabit the swampy forest zones in Nigeria but could inhabit drier regions. Some are arboreal and digitigrades, characterized by long bare tails and opposable thumbs modified for climbing and grasping respectively, they are known to be deficient in comparative sociality, peculiar brain morphology and a short life span. Our aim was to correlate through macro-neuromorphometry as well evaluate for the influence of head and brain weight, sex, adaptation, and behavioral ecology on the brain dimensions in comparison with other marsupials. Method: This study utilized thirteen animals (didelphys marsupialis cancrivota) consisting of four (6) males and seven (7) females and employing statistical methods in making inferences among the categories. Results: The mean overall head weight was 256.17 ±54.11g, 250.60± 51.62g for females and 269.16 ±139.22g for males, the whole brain weight was 30.43 ±10.19g. The brain /head weight ratio was 0.05± 0.02 while the maximum cerebral diameter, length and height were 46.97 ±13.84mm, 48.01±19.72mm and 30.48 ±2.90mm. cerebellar weight was 1.81 ±1.09g, and the cerebellar height and width were 2.39 ± 0.38mm and 2.44 ± 1.59mm respectively, cerebrum/ whole brain length index was 0.86± 0.04mm while mean endo-cranial volume was 19.75 ±30.11mls.The sexually dimorphic variables include whole brain length (59.87± 9.56mm and 57.12± 12.01mm), cerebral length (49.93± 10.17mm and 41.12± 15.57mm) and cerebral diameter (35.91± 13.55mm and 43.54± 29.96mm) for females and males respectively, suggesting better encephalization in females of this species compared to the males. Also, dimorphic parameters function for purposes such as predatory instincts, nursing of the young, spatial orientation, migrations and ecologic adaptations. Conclusion: In addition, this investigation suggests the enhanced possibility of cerebro-vascular accident in this species partly due to the cerebral length and height ratio in relation to the endo-cranial volume and shape in the likelihood of shorter lifespan in the males.