The conjugated linoleic acid (CLA) trans-10,cis-12 inhibits fat synthesis in the mammary gland of bovines, ewes, and goats, at least in part, by regulating the expression of genes involved in lipid metabolism. However, in sows, studies about CLA regulation of lipogenic gene expression are scarce. The objective of this study was to evaluate the effect of trans-10,cis-12 CLA on mammary and adipose lipogenic gene expression of sows. Twenty multiparous commercial line sows with a mean body weight (BW) of 200 ± 10 kg were randomly assigned to one of the 2 treatments (n = 10/treatment) for 18 d: 1) Control (no CLA added) and 2) CLA at 1% of diet DM (29.9% of trans-10,cis-12 and 29.8% of cis-9,trans-11) mixed in the ration. The diet was formulated to meet the nutritional requirements, the sows were kept in a controlled environment (temperature, humidity and ventilation) and the CLA treatment was administered from d 7 through d 25 of lactation. Mammary and adipose tissue biopsies were taken on d 25 of each experimental period for subsequent RNA extraction and analysis of gene expression by SYBR Green Real-Time RT-PCR. Data were analyzed as a complete randomized design using the Mixed Procedure of SAS. CLA reduced mammary expression of all lipid enzymes evaluated (ACACAα: −37%, P = 0.003; FASN: −64%, P = 0.002; SCD1: −52%, P = 0.003; LPL: −26%, P = 0.03; AGPAT6: −15%, P = 0.02; and DGAT1: −27%, P = 0.02), except FABP3 (P = 0.09). Mammary expression of milk proteins, β-casein and α-lactalbumin, were reduced by the CLA treatment (P = 0.0004 and P = 0.005, respectively), compared with Control. CLA treatment had no effect on expression of the same lipogenic genes in adipose tissue. As in ruminants, in sows mammary expression of genes involved in the evaluated lipogenic pathways were reduced by CLA, and a greater magnitude was observed in genes from the de novo pathway synthesis