Research on the zinc status of osteoporotic women is scarce. This randomized, double-blind, placebo-controlled clinical trial assessed the effect of zinc supplementation on serum zinc and calcium levels in postmenopausal osteoporotic women. A sample of 60 women referred to a rheumatology clinic in Tabriz were randomly divided into intervention (220 mg zinc sulfate daily) and placebo groups. Anthropometric indices, dietary intake of zinc and calcium and serum zinc and calcium were assessed at baseline and after 60 days. Mean serum zinc concentrations were markedly lower than the normal range at baseline, but mean serum calcium levels were normal. In the intervention group serum levels were significantly higher after 60 days [120.5 (SD 7.5) versus 70.5 (SD 4.6) micrograms/dL] while serum calcium levels were unchanged [8.6 (SD 0.1) versus 9.1 (SD 0.3) mg/dL]. The placebo group showed no significant changes in zinc or calcium levels. Postmenopausal osteoporotic women may benefit from zinc supplementation.