As the rest of the tuna, albacore does not show apparent sexual dimorphism in colour pattern or external morphological characters.

Spawning
They are multiple or batch spawners, shedding batches of hydrated oocytes, in separate spawning events, directly into the sea where fertilization occurs. There is a close relationship between spawning and sea surface temperature: temperatures above 24ºC and a deep thermocline seem to stimulate maturation and reproductive activity in tunas. Apparently, spawning might be synchronised with high temperatures in order to enhance growth of eggs and larvae.

Spawning occurs in roughly the same offshore environments they normally inhabit. Albacore spawning areas in the Atlantic are found in subtropical western areas of both hemispheres and throughout the Mediterranean Sea.
Spawning grounds of the North Atlantic stock are found in waters offshore Venezuela, Sargassum Sea (Le Gall 1974, Nishikawa et al 1985) and Gulf of Mexico (Richards 1969, 1984). In the South Atlantic, spawning occurs off the eastern Brazilian coast during the austral summer (Beardsley 1969, Koto 1969). In the Mediterranean, larvae have been found in several parts of the basin by numerous authors (Dicenta 1975, Lalami et al 1973, Piccinetti and Manfrin 1993, García et al 2002).

Spawning takes place during austral and boreal spring-summer. In the North Atlantic, reproduction events take place from April till September and some larvae are even found in the winter (Richards 1969,1984), but the peak of spawning occurs around July.

Nocturnal spawning seems to be common among scombrids (as well as other groups of fishes) although there is not such evidence for albacore (reviewed in Schaefer 2001).

Eggs and larvae
Postel (1964) estimated fecundity in 2-3 million eggs per female. Eggs are pelagic, spherical and transparent. Smaller than those of other tuna such as Thunnus thynnus, they are 0.84-0.94 mm of diameter and contain an oil globule of 0.24 mm of diameter. Yolk is homogeneous (Sanzo 1933).
Yolk-sac larvae are typically 2.5 mm when they hatch. Their differential characteristic, compared with the rest of tunas, is the lack of pigment in the caudal region (Nishikawa and Rimmer 1987).

Recruitment
Knowledge of the early life stages in tunas is very scarce. It is assumed that larval period is short. The beginning of the juvenile period has been established arbitrarily as to sizes escaping from plankton nets, around 2 cm (Bard 1981).
From 2 to 35-40 cm FL, juvenile tuna are not caught nor by plankton nets, commercial fishing or gamefish. Therefore, this life stage remains virtually unknown.
Young (immature) albacore first appear in surface catches when they are around 40 cm fork length. From this time on, it is easier to know their migratory movements both by observing the fisheries and by tagging experiments.