Individual growth histories of the shortfin squid Illex argentinus were reconstructed in 1512 individuals obtained during seven years of commercial exploitation in southern-south-eastern Brazil. Growth increments were directly measured on the gladius dorsal surface from the anterior part to posterior end in two-thirds of the entire length. Gladius growth increments were deposited at the same rate as statolith rings and the daily nature of the growth increments was supported. Because gladius length is strongly related to mantle length, growth increments closely approximated mantle length growth rates, allowing the reconstruction of both size- and age-dependent growth. Individual reconstruction was possible between 4 and 347 mm of gladius length, almost the entire life cycle of the species. The variability of the acceleration in gladius growth evidenced four life history transitions where the most noticeable occurred between paralarval/juvenile stages, delimiting male/female size differentiation. The changes in acceleration in growth throughout the size-range may be influenced by the thermal gradients experienced by individuals during life history events transitions in Brazilian waters.