This chapter deals with seed maturity, longevity, and changes during seed deterioration in Dalbergia sissoo. During maturation, pod colour changed to light brown at 225 days after anthesis (DAA). Physical, physiological, and biochemical changes enabled the seeds to attain germinability by 195 DAA, though full maturity was attained by 240 DAA. Mature seeds were stored for 665 days under different conditions, including various storage temperatures (40, 25, 15, 5, –5 °C, and room temperature), seed moisture contents (12.5%, 8.0%, and 5.6%), and storage containers (vacuum boxes, polythene bags, and plastic boxes). The storage behaviour indicated that D. sissoo seeds exhibit orthodox characteristics, maintaining up to 86% viability when stored at –5 °C with 5.6% seed moisture content under sealed conditions. The survival curve and viability loss rate (-V/D) revealed that reducing seed moisture content and storage temperature enhanced seed longevity. The seeds underwent physical, physiological, and molecular changes with deterioration, ultimately losing viability. Seed colour changed from light brown to dark brown, seedling length declined from 9.07 cm to 0.00 cm, and electrical conductivity and respiration increased from 0.10 to 0.58 mhos/g and 0.05 to 0.27 µmho/mg/s, respectively. A decline in starch, sugar, and protein content and complete cellular disintegration further contributed to the loss of seed viability.