Abstract: This study assessed the effectiveness of anti-poaching activities as it tends to curtail the rate of different forms of threats facing biodiversity conservation in Old Oyo National Park between 2001 and 2015. Data was obtained from administrative records of the park for the period and analyzed using descriptive statistics and least square regression. The results showed irregular trends in park expenditure, park staff and arrest of poachers with an annual mean of ₦119,876,868.70 ($328,429.78), 229.8± 36.46 and 95.2±33.76 respectively. The results also showed variation in the rate of poacher’s arrest across the various ranges in the park with Oyo-Ile range having the highest number (454) of arrest, grazing in the park had the highest number of offenders being arrested (682) and majority of the poachers’ offences were compounded (970) during prosecution. The study recommends adequate funding to ensure that protection officers are well equipped and motivated to ensure a higher productivity and also modalities be put in place to ensure apart from arrest and prosecution of offenders, a partnership with the support zone communities is achieved to ensure effective biodiversity conservation in the park.