Two field experiments were conducted on the Teaching and Research Farm of the Federal University of Agriculture Abeokuta (7° 15′ N 3° 25′ E altitude 140 m above sea level) in south western Nigeria between June and November 2012 to evaluate the performance of two sunflower varieties (SAMSUN-3 and Funtua) as affected by different sowing dates and organic fertilizer application. The experiment was laid out in split'split plot design with sowing dates as main plot organic fertilizer as sub-plot and variety as sub-sub-plot and replicated three times. Sowing date significantly ( P ≤0.05) increased and reduced number of phenological days to flowering of early and late sown sunflower respectively. Funtua (a local adapted variety) matured 7 days later than SAMSUN-3 (recently released variety) when sown late. Application of organic fertilizer significantly ( P ≤0.05) increased plant height of early and late sown sunflower. Delay in sowing till first week in September significantly ( P ≤0.05) reduced head diameter number of seeds per head and seed yield of late sown sunflower. Oil and protein contents of seeds from early and late sown sunflower plants were significantly ( P ≤0.05) increased by organic fertilizer application except protein content of late sown sunflower. However it significantly ( P ≤0.05) increased oil yield by 23% relative to the control in the late sown sunflower. Based on the comparatively high seed yield (850.45'1525.78 kg/ha) recorded in our study it is recommended that sunflower be sown in the forest'savanna transition zone in early July or second to third week in August.