This study examined farmers’ and extension personnel's View of constraints to effectiveness of agricultural extension services in Oyo State. Simple random sampling technique was used to select 100 farmers and 20 extension personnel. Data subjected to descriptive and correlation analyses were collected using questionnaire and interview schedule. Findings reveal that constraints to effectiveness of extension service include inadequate extension equipment ( = 3.73), insufficient extension personnel ( = 3.44) and poor planning of extension programme (= 2.8). About 54% of farmers perceived that extension service is ineffective while about 46% of extension personnel perceived it to be effective. Results show a weak correlation between personal characteristics of farmers and their perception towards the effectiveness of agricultural extension services (r = 0.081, p< 0.05). It is concluded that constraints to effective extension service might not significantly affect the peoples’ view of extension effectiveness, however, the less the constraints to extension services the better the perception of extension services