The study was conducted at Instructional-cum-Research Farm of Department of Horticulture, Indira Gandhi Krishi Vishwavidyalaya, Raipur (C.G.) during rabi season (2012-13) to study the effect of seedling age and transplant density on growth and yield of onion variety Agrifound Light Red. The result indicated that the advancement in seedling age from 60 days to 30 days significantly increased growth and yield attributes viz., plant height, pseudostem length and width, equatorial and polar bulb diameter, average bulb weight and total bulb yield. It was further observed that with the increase in transplant density from 44 plant m-2 (15 x15 cm) to 100 plant m-2 (10 x10 cm), a significant increase in plant height, pseudostem length, polar bulb diameter and total bulb yield and a significant decrease in number of leaves per plant, pseudostem width, equatorial bulb diameter and average bulb weight was noticed under the present study. Interaction studies indicated significant improvement in total bulb yield of older seedling under higher plant density.