Aggregatum onion (Allium cepa var. aggregatum) is mainly grown in Tamil Nadu, Andhra Pradesh and Karnataka. In TamilNadu it is cultivated in an area of 30,000 ha. It is well known for its use in sambar preparation, an important South Indian dish. It has demand in the international market due to its unique taste and flavor. The bulbs are produced in clusters and are smaller in size compared to the bellary onion. The present study was conducted at the College Orchard of the Department of Vegetable Science, Horticultural College and Research Institute, Tamil Nadu Agricultural University, Coimbatore during 2021-2022. A total of 65 genotypes maintained at the Department of Vegetable Science were evaluated for yield, quality parameters, and disease index. Observations were recorded on Average bulb weight (g),Total Soluble Solids (%),Total Yield (t/ha),thrips damage(%), leaf spot (PDI) and Stemphyllium blight (PDI).Among the different genotypes evaluated for the performance of aggregatum onion, significant differences were observed for all the traits studied. Average bulb weight was the highest in the genotype, Agg-Sel-1 with 66.2g followed by Agg-Sel-3 with 64.4g.The genotypes, Agg 1522 and Agg 1692 recorded a total yield of 17.4t/ha which was higher than all other genotypes. The highest percent of Total Soluble Solids (15.3) was recorded in Agg1552 followed by Agg 1535 with 15.2% and Agg-Sel-4 with 15.0%.The genotypes evaluated also showed significant differences for disease scoring. The lowest percent of thrips (12.5) was observed in Agg 1528, the lowest leaf spot incidence was observed in Agg1532 with 11.5 and the lowest incidence of Stemphyllium blight was recorded in Agg-Sel-2 with 3.7.The genotypes showing better performance can be utilized for further breeding programmes.