Context Meat tenderness is affected by numerous factors that can cause considerable economic loss as it is one of the characteristics of meat most appreciated by consumers. Higher expression of the calpastatin gene (CAST) has been associated with a reduced meat tenderness in different animal species. Aims Our main objective of the present study was to evaluate the association of the expression of the CAST gene with the shear force of goat muscle. We also assessed whether variations in gene expression could be explained by the polymorphism already identified by other authors or whether the polymorphism may be associated with phenotypic characteristics such as meat tenderness, slaughter weight and carcass weight. Methods Forty crossbred goats (Saanen × Alpine) were slaughtered at ~150 days of age. So as to obtain the genotype of each animal, blood samples were collected on the day of slaughter for subsequent DNA isolation. On the same day, samples of muscle tissue (Longissimus lumborum) were collected to analyse both gene expression and shear force. Key results Among the seven alleles already known from A to G, the C allele, which is the only one exhibiting exon variation, was not observed in our samples. We found, for the first time, that in goat, the highest CAST-gene expression levels are directly related to an increase in the muscle shear force, as has been described for other species. No statistical difference was observed for shear force, slaughter weight or carcass weight among the different genotypic groups evaluated. However, we observed that the level of expression of the CAST gene within Group 7 (Genotypes GG and GE) presented a higher value that in the other genotypes (P < 0.05), although we did not find a satisfactory explanation for the increase in expression in those genotypes. Conclusions Our results gave support what has already been verified in studies with other species, namely that the calpastatin-gene expression is related to the postmortem meat-tenderising process. Implications The tenderness is an important feature in the choice of meat. Several factors can alter this characteristic, such as breed, age, sex and slaughter weight of animals. The molecular mechanisms involved in ante-morten and postmortem processes are important for improving understanding of how we can identify animals that tend to have softer meat after slaughter by applying new technologies, such as molecular marker.