Background Anxiety symptoms are pervasive among elderly populations around the world. The Geriatric Anxiety Inventory (the GAI) has been developed and widely used in screening those suffering from severe symptoms. Although debates about its dimensionality have been mostly resolved by Molde et al. (2019) with bifactor modeling, evidence regarding its measurement invariance across sex and somatic diseases is still missing. Methods This study attempted to provide complemental evidence to the dimensionality debates of the GAI with Mokken scale analysis and to examine its measurement invariance across sex and somatic diseases by conducting differential item functioning (DIF) analysis among a sample of older Chinese adults. The data was from responses of a large representative sample (N = 1314) in the Chinese National Survey Data Archive, focusing on the mental health of elderly adults. Results The results of Mokken scale analysis confirmed the unidimensionality of the GAI, and DIF analysis indicated measurement invariance of this inventory across individuals with different sex and somatic diseases, with just a few items exhibiting item bias but all of them negligible. Conclusions All these findings supported the use of this inventory among Chinese elders to screen anxiety symptoms and to make comparisons across sex and somatic diseases.