Chronic low-grade inflammation plays a role in the pathogenesis of several chronic diseases including cancer. Physical activity (PA) and diet have been supposed to modulate inflammatory markers. We evaluated the effects of a 24-month dietary and/or PA intervention on plasma levels of pro-inflammatory cytokines, a secondary analysis in the DAMA factorial trial. The 234 study participants (healthy postmenopausal women with high breast density, 50-69 years, non smokers, no hormone therapy) were randomised to four arms: (1) isocaloric dietary intervention mainly based on plant-foods; (2) moderate-intensity PA intervention with at least 1 h/week of supervised strenuous activity; (3) both interventions; (4) general recommendations on healthy dietary and PA patterns. Interleukins (IL)-1α, -1β, -6, tumor necrosis factor-α and C-reactive protein were measured at baseline and at the end of the intervention. Intention-to-treat-analyses were carried out using Tobit regression. Although all cytokines tended to increase over time, after 24 months women in the PA intervention (arms 2 + 3) showed lower levels of IL-1α (exp(β) = 0.66; p = 0.04) and IL-6 (exp(β) = 0.70; p = 0.01) in comparison with women in the control group (arms 1 + 4). No effects of the dietary intervention emerged. In healthy postmenopausal women with high breast density a moderate-intensity PA appears to slow the age-related increase of pro-inflammatory cytokines.