This study investigated the effects of the administration of long chain omega-3 fatty acids (ω-3 FA) and acetylsalicylic acid (ASA) on inflammation, performance, and fertility in periparturient dairy cows. Five weeks before calving, 26 multiparous dairy cows were randomly assigned to 1 of 3 treatments: ω-3 FA (n = 9; OME), ω-3 FA and ASA (n = 9; OMAS), or palm oil (n = 8; CTR). During the last 3 wk of pregnancy, OME and OMAS groups received daily 12.0 g of fish-derived ω-3 FA, whereas CTR cows received only SFA. In addition, OMAS cows received daily 6.0 mg ASA/ kg BW starting at 7 d before calving. Only a few cows had health problems after calving, but those in OMAS were most affected (n = 3 vs. 1 in CTR). Inflammatory status around calving did not improve in OME cows, as confirmed by the patterns of concentration of acute-phase proteins (APP), which were similar to CTR. Compared with CTR and OME, the increase of the positive APP and the decrease of the negative APP (e.g., albumin; P < 0.01) observed in OMAS cows suggested a severe inflammatory status after calving. Compared with OMAS, postcalving energy metabolism was better in OME cows as shown by a lower degree of lipomobilization (smaller BCS drop, greater glucose) and milder ketogenesis (less β-hydroxybutyrate; P < 0.01). Cows in CTR had optimal fertility indices, whereas OMAS was the worst group. The severe inflammation and the more negative energy balance likely contributed to the poor fertility parameters in those cows. It is known that ASA exerts an inhibitory effect on cyclooxygenases, causing a possible decrease in the synthesis of PGF2α. A decreased concentration of PGF2α is connected with alterations in the physiologic processes related to labor and to uterine motility. Cows in OMAS had a longer pregnancy (P < 0.10 vs.OME) and a greater frequency of retained placenta, which may be attributed to decreased synthesis of PGF2α. The administration of ω-3 FA alone did not delay calving or the expulsion of fetal membranes. In conclusion, long-chain ω-3 FA improved the physiological status of cows, partly through better energy balance. The administration of ASA before calving (even at a low dose) in combination with ω-3 FA did not exert any synergistic positive effect on inflammation and performance. © 2013 American Society of Animal Science. All rights reserved.