The goal of our study was to determine the efficacy of Farabloc, an electromagnetic shielding fabric compared to placebo fabric when worn as a nightgown, as an analgesic in patients hospitalized with fibromyalgia. In a rheumatologic and rehabilitation hospital, we performed a phase 1, single-blind study of patients using Farabloc (F) or placebo (P) gowns for 8 h per night during the 20-day hospitalization and a phase 2, single-blind crossover study of patients using both F and P gowns randomly and alternatively switching after 10 of 21 days hospitalization (phase 1: 42 F, mean age 49.02 years, 35 female, 7 male; 84 P, mean age 48.08 years, 72 female, 12 males; phase 2: 25 F/P, P/F, or P/P, mean age 44.0 years, 24 female, 1 male). The study involved randomly selected and blinded use of hospital gown 8 h per night of either F or P fabric. The main outcome measures were changes from admission or midpoint to discharge in quantity of pain (QN), quality of pain (QL), and paracetamol use (PU). In phase 1, all three variables significantly favored F over P when using paired t test, two sample t test, Mann-Whitney, and analysis of covariance tests. QN was reduced (F = -2.03 -/+ 0.99*, P = 0.59 -/+ 0.71). QL was reduced (F = -10.64 -/+ 5.69*, P = -2.54 -/+ 3.40). PU was reduced (F = 10.69 -/+ 6.68*, P = 26.12 -/+ 9.37). In phase 2, comparing midpoint to discharge levels in the three variables again favored P/F over F/P and P/P (>0.001): QN (P/F +16.00 -/+ 8.35* F/P -13.27 -/+ 11.40), QL (P/F +8.71 -/+ 4.75* F/P -6.55 -/+ 5.59), and PU (F -9.29 -/+ 4.39* P -18.00 -/+ 5.27) (*p = <0.001). Patients with fibromyalgia had less pain after sleeping in a gown made of Farabloc than with a placebo fabric. This suggests that Farabloc, an electromagnetic shielding fabric, has analgesic properties in fibromyalgia. Reduced pain observation is consistent with previous studies in phantom limb pain and delayed onset muscle pain. Limitations of this study include single blind design, small sample size, and in phase 2, a lack of washout period and a F/F group.