The growing preference for 'Hass' avocado on a worldwide scale has encouraged the release of new cultivars as well as their evaluation under different soil and climatic conditions. The cultivar 'Carmen Hass', resulting from a spontaneous mutation, achieved excellent performance in Mexico and South Africa, producing fruits earlier than 'Hass' trees and allowing commercialization during periods of high market prices. The objective of this research was to compare the performance of 'Hass' and 'Carmen Hass' avocado trees under the soil and climate conditions of southeast region Brazil. The climate of region is subtropical humid with dry winter. Between the fourth and fifth year after planting, plants were evaluated for flowering (panicles branch-1, percentage of determinate and indeterminate inflorescences), fruit maturation (dry matter content), yield (kg plant-1, fruits plant-1), yield efficiency (kg m-3), morphological characteristics of fruit (weight, length, diameter, length/diameter ratio), and postharvest quality (pulp firmness, occurrence of pulp discoloration, chilling injury, vascular browning, lenticel damage, and skin color change). Fruit size, shape, and postharvest quality were also evaluated in the sixth year after planting. 'Carmen Hass' is a promising alternative for producing 'Hass'-type avocados, reaching physiological maturity sooner and allowing harvesting 15 days earlier than 'Hass'. Its higher proportion of indeterminate inflorescences contributed to greater yields, although resulting in smaller fruits, and no off-blooming was observed under the conditions of this study. Postharvest performance was comparable between cultivars, with 'Carmen Hass' maintaining firmer flesh after 21 days and showing reduced vascular browning after 28 days of storage.