This study determined a tylosin concentration in swine wastewater located in a Mexican pig farm, during different stages of the pigs' growth. The detection of antibiotics in swine wastewater is complex due to its high concentration of solids. Analytical method was developed for detection of tylosin in swine wastewater and swine slurry. Average recoveries of tylosin in the liquid and solid phase were greater than 51 and 44%, respectively, with a greater total recovery of 95%. The results indicated the presence of tylosin in swine wastewater and slurry at concentrations greater than the ones reported in the literature. In grab samples of swine wastewater, the tylosin detected showed concentrations of 56, 72 and 8.6 μg L−1, in breeding-gestation, nursery pigs, and grow-finishing area, respectively. In composite samples, the concentration of tylosin was 11.8 μg L−1 for the breeding-gestation area and 2.4 μg L−1 for the grow-finishing area. For slurry, the concentration of tylosin was 20.6 and 17.8 μg L−1, for the breeding-gestation and grow-finishing area, respectively. This study presents the detection of a high concentration of tylosin in breeding-gestation and nursery pigs. Traces of tylosin in wastewater from grow-finishing stage were found although the animals were not receiving antibiotics.