This study was aimed at investigating the bioefficacy of organic compared with inorganic manganese (Mn) for eggshell quality. An amino acid-Mn complex or Mn sulfate monohydrate was used as the organic or inorganic Mn source. A total of six hundred forty-eight 50-wk-old layers (Hy-Line Brown) were divided into 9 groups; each group consisted of 6 replicates with 12 layers each. The feeding trial lasted 12 wk. During the first 4 wk of the feeding trial, the groups were fed a basal diet, which met the nutrient requirements of the layers, except for Mn. During the following 8 wk, 9 levels of Mn (inorganic Mn: 0, 25, 50, 100, and 200 mg/kg; organic Mn: 25, 50, 100, and 200 mg/kg) were used to supplement, respectively, in the basal diet on an equimolar basis. An exponential regression model was applied to calculate the bioefficacy of organic Mn compared with the inorganic Mn. Dietary supplementation with either organic or inorganic Mn did not influence egg production and feed efficiency of (P > 0.05), and eggshell quality did not exhibit a significant response to dietary supplementation with Mn sources at 56 and 58 wk (P > 0.05). Dietary supplementation with either organic Mn or inorganic Mn significantly enhanced the thickness, breaking strength, and elastic modulus of the eggshells compared with the control group at the end of 62 wk (P < 0.05). At the end of 62 wk, the bioefficacy of organic Mn was 357% (shell thickness), 406% (breaking strength), 458% (elastic modulus), and 470% (eggshell Mn), as efficacious as inorganic Mn at equimolar levels. This study suggests that organic Mn enhances eggshell quality in aged laying hens compared with inorganic Mn.