Blanket dry cow therapy is a common preventative measure of mastitis control. However, concerns over antimicrobial resistance, may lead to concerns over blanket therapy as an unnecessary use of antimicrobials. Selective dry cow therapy involves only administering antimicrobials to those cows that require them at dry-off to cure existing infections. This research was conducted at 3 Irish research herds between 2015 and 2017. Prior to dry-off, weekly milk recording data were used to identify cows which had not exceeded 200,000 somatic cells at any point in lactation and to randomly assign them to 1 of 2 treatments: (1) antibiotic plus teat seal (AB&TS), or (2) teat seal only (TS). SCC was analyzed as (1) average, (2) minimum, and (3) maximum animal SCC across lactation, and as (4) test-day SCC. Analyses were conducted using records from the first 3 wk and first 120 d of lactation. The effect of treatment was quantified using a repeatability model accounting for concurrent experiment treatment level, breed (proportion of Holstein, Jersey, or Norwegian Red), heterosis, recombination, month of calving, parity (n = 4; 1, 2, 3, 4+), year (n = 3). For SCC traits with a single lactation value animal was repeated across years of the study. Animal was repeated across lactation week when the dependent variable was test-day SCC. The likelihood of having an SCC reading ≥ 200,000 was quantified using logistic regression adjusted for the same fixed effects as the linear model. Up to 56% of cows in the research herds (n = 364 lactations) were eligible for inclusion in the analyses. The minimum, maximum, and test-day SCC of TS only cows was greater than those cows that received AB&TS both in the first 3 wk and 120 d of lactation (P < 0.05). TS only cows were 2.9 times more likely to have an SCC reading > 200,000 within the first 120 d of lactation. However, the majority of cows (>80%) in both treatments maintained SCC < 200,000. Administering TS only to cows that have not had high SCC throughout lactation may offer a viable method to reduce on-farm anti-microbial use while not affecting herd-level SCC.