The present study addressed the reproductive biology of the horse mackerel, Trachurus trachurus, in the northern area of the Moroccan Atlantic between December 2015 and November 2016, to provide more biological elements for stock management and good analysis of population dynamics. Monthly monitoring of the gonado-somatic index (GSI), the condition factor (K) and the stages of sexual maturity in the horse mackerel revealed that it is in reproductive activity during the period from January to June, with a peak spawning in February for females, and January for males. In addition, the length of the first sexual maturity was estimated at 21.75 cm (TL) for males and 22.75 cm (TL) for females. The evolution of the sex ratio showed a dominance of females overall size classes and during all seasons with an overall value of 0.58. The determination of fecundity allowed to assess that the total fecundity varies between 11424 and 114464 eggs with an average of 49072 ± 25045. For the relative fecundity, it varied between 159 and 770 eggs per gram of total weight, with an average of 426 ± 132, for a total length interval of 19 to 32.5 cm.