Prevention of mastitis is a priority for the dairy industry. Once pathogens invade the mammary gland, resident macrophages are the first line of defense. Thus, they can be a target to aid in prevention of intramammary infection (IMI). Macrophages can be activated through 2 major pathways: classical activation (C) which releases pro-inflammatory cytokines and alternative activation (A) with the production of anti-inflammatory cytokines. TNFα and NOS2 are markers of the C while IL-10 and TGF-β are markers of the A activation of macrophages. Peroxisome proliferator-activated receptor γ (PPARγ) is expressed in human macrophages and it is known to activate the A pathway. The activation of A by PPARγ has not been tested in ruminants but may affect the response to IMI. This study aimed to evaluate the effects of PPARγ activation by the putative PPARγ agonist 2,4-thiazolidinedione (TZD) on the activation of macrophages during subclinical mastitis in dairy goats. To test this, 12 lactating goats received daily injections of either TZD (n = 6) or saline (n = 6, CTR). Following 14 d of treatment, all goats received an intramammary infusion of Streptococcus uberis to induce subclinical mastitis in the right half of the mammary gland while the left half served as control. Macrophages were isolated at 5 d post-IMI from 250 mL of milk using immunomagnetic sorting. Expression of genes markers of the C and A pathways on macrophages was assessed via RTqPCR. Data were analyzed by GLIMMIX of SAS. Significance was declared at P < 0.05. Abundance of transcripts related to the classical macrophage activation (NFKB1, IL8, and CCL2) was increased by mastitis but no effect was detected on TNFA. Expression of the markers for alternative activation of macrophages, IL10, was not affected whereas TGFβ1 tended to be increased by mastitis (P = 0.06). No effects were observed on expression of measured genes by TZD with the exception of a tendency (P = 0.09) for a lower IL4 expression. Thus, our findings do not support the alternative activation of macrophages in the mammary gland of dairy goats by PPARγ.