Achachairú is a tropical fruit that is being evaluated for its potential as a new fruit crop for Puerto Rico. More information is needed concerning postharvest aspects of this fruit. In this paper we describe the physical and chemical characteristics of achachairú during storage at ambient temperature. During each of three harvest years, 75 to 100 fruits were harvested, washed and dried, then divided into five groups. Each group was placed in an open cardboard box and randomly assigned to one of five storage treatments (0, 5, 10, 15, and 20 days at 25 ± 2 °C, 75 ± 5% relative humidity). Physical and chemical properties, including sugar content, were determined for each storage period. Sensory panels evaluated fruits after 0 and 15 days of storage. Over the 20-day storage period fruit weight, size (length and diameter), firmness and pulp weight decreased by 1.5% to 2.5% per day. The rating of external fruit appearance (evaluated on a hedonic scale) deteriorated in a curvilinear fashion over time, initially changing little, and then showing increased deterioration (dark spots and wrinkling) starting at 15 days post storage. Total soluble solids (°Brix) (TSS) increased over time by 0.8 to 1.6% per day, while total titratable acid (TTA) decreased 1.4 to 3.0% per day, resulting in an increase of the sugar-acid ratio (TSS/TTA) of 2.1 to 12.4% per day over 20 days of storage. Sucrose was the most abundant sugar (7.19 g/100 g), followed by fructose (3.38 g/100 g) and glucose (3.18 g/100 g). Panelists judged the sweetness, aroma, acidity, juiciness and overall flavor not to have changed after 15 days of storage. Results of this study suggest that achachairú can be stored at ambient temperature for 15 days and maintain fruit quality acceptable to the consumer.