The objective was to compare the reproductive performance of liquid sex-sorted (SS) semen with that of conventional (CON) semen in lactating dairy cows. Between 2011 and 2013, selected dairy herds were allocated with liquid SS semen at 50% of the daily requirement and the remaining daily requirement was allocated with CON liquid semen. Sperm for producing SS semen was sorted by Sexing Technologies NZ Ltd and then packaged using LIC’s liquid semen technology at a dose rate of 1 × 10⁶ sperm. Artificial insemination (AI) with liquid SS semen was carried out between 43 and 46 h after collection. CON semen straws contained 1.25, 1.75 or 2 × 10⁶ sperm for semen to be used on Day 1, 2 or 3 after collection, respectively. Only CON inseminations on the same days as when SS semen was used were included in the comparison. The least-squares means estimate for the difference in non-return rate between AI with SS and CON semen over 3 years was -3.8 percentage points (SS = 70.2% vs. CON = 74.0%; SS/CON = 0.949). The estimated difference in calving rate per AI between SS and CON semen was ‑3.1 percentage points for 2011 (SS = 51.2%; CON = 54.3%; SS/CON = 0.943) and -3.0 percentage units for 2012 (SS = 49.7%; CON = 52.6%; SS/CON = 0.945). The percentage of heifer calves born to AI with SS semen was 87.0% for 2011 and 85.8% for 2012, both of which were lower than the expectation of 90% mainly due to misidentification of calf dams in seasonal dairy herds calving on pasture. In summary, results showed that liquid SS semen only required half the dose rate of frozen SS semen to achieve a reproductive performance of over 94% of CON semen in lactating dairy cows.