Growth, mortality and sexual size dimorphism of Vipera latastei were investigated in northern Portugal. Size structure ranged from 16–58 cm of snout–vent length (SVL), with peaks between 40–45 cm for males and 35–40 cm for females. Age structure ranged between 0 and 14 years, with peaks at 4 and 5 years for males and at 4–6 years for females. Longevity was 11 and 14 years for males and females, respectively. Sexual maturity was attained approximately at four years in males, and one year later in females, however, at a similar body size. Growth rates decreased with increasing SVL; males grew faster than females at all ages; and asymptotic body size was larger in males than in females. Mortality was higher in males than in females and increased after sexual maturity in both sexes. The sexual differences in mortality annulled an age-specific sexual size dimorphism in favor of males and produced a minor sexual size dimorphism in mean adult body size of V. latastei.