Prostate cancer is a major public health issue in men in their advancing years. Huggins and colleagues demonstrated the relationship between testicular androgen (testosterone) and prostate cancer growth. Since then, a lot more had been done in this area of study. Recently, low serum level of testosterone had been linked to aggressive prostate cancer (Pca). We set out to investigate the relationship between low serum testosterone and parameters related to Pca aggressiveness. Materials and Methods: We retrospectively studied fifty-one (51) men diagnosed with Pca who also met the inclusion criteria. Case-notes of these men were retrieved and relevant information for the study were extracted and entered into a spread-sheet and analyzed using the Statistical Package for Social Sciences (SPSS) version 20.0 software. Results: The mean age and standard deviation for all men was 68.51±7.179 years ranging from 52 to 88 years. Men with low serum testosterone were older. Mean prostate specific antigen (PSA) and Gleason score (GS) were 45.90±30.95 ng/ml and 8.04 ±1.038 respectively; both indicating features of aggressive Pca. Mean serum testosterone was 3.741±1.938 and this correlated inversely with serum PSA and GS. Conclusion: Serum testosterone correlated inversely with notable parameters of aggressive Pca.