Inflammation in older persons is associated with frailty, cachexia, and disability. We hypothesized that NSAID treatment in addition to antibiotics in older patients with acute infection might rapidly reduce inflammatory cytokines and might be of therapeutic potential to improve outcomes. A double-blind controlled trial was conducted in geriatric patients admitted for acute infection. Patients were randomized to receive either 10 mg piroxicam or placebo. Patients ≥70 years with CRP levels >10 mg/L of acute infectious origin were eligible. Twenty-five cyto-/chemokines as well as heat shock proteins Hsp27 (HSPB1) and Hsp70 (HSPA1A) were measured the first 4 days and then weekly until discharge, with a maximum of 3 weeks. Thirty Caucasian patients were included (median age 84.5 years, 67% female, median CRP 87.5 mg/L). In the piroxicam group, IL-6 and IP-10/CXCL10 decreased significantly during the study period. Relationships between cytokines were disrupted in the piroxicam group: for 12 out of 20 cytokines the number of correlations between changes in serum levels was significantly lower compared to placebo. Serum Hsp70 levels decreased significantly in the piroxicam group, but not in the placebo group. Without heat challenge, intracellular levels of Hsp70 in monocytes decreased in both groups, whereas HsP27 in monocytes increased with piroxicam with a significant difference compared to placebo at 3 weeks. Piroxicam in this setting cannot be considered merely as an anti-inflammatory drug, but rather as an immunomodulator. Further studies are needed to establish whether these effects can change functional outcomes in geriatric patients.