Aluminum alloys have been widely applied in coastal and marine structures because of their superior sustainability and corrosion resistance. Concrete-filled double-skin aluminum tubular columns (CFDAT) possess higher strength and better ductility than traditional reinforced concrete structures. However, few studies have been conducted on numerical simulation methods for circular CFDATs. Specifically, there has been no experimental or numerical study on intermediate-to-slender circular CFDATs. Here, a comprehensive numerical study was conducted on a modeling method for the first time to simulate the axial behavior of a slender circular CFDAT. This study outlines the development of numerical modeling techniques and presents a series of comparative studies using various material nonlinearities, confinement effects, and nonlinearity of the initial geometric imperfections for a slender column. The numerical results were compared with more than 80 previously available stub and slender experimental test results for verification. It was confirmed that the proposed numerical technique was reliable and accurate for simulating the axial behavior of intermediate and slender circular CFDAT. Furthermore, a parametric study was conducted to investigate the effects of geometric and material properties on the axial capacity of the CFDAT. Additionally, the slenderness and strength-to-width ratio of CFDAT were compared with those of concrete-filled double-skin steel tubular columns (CFDST). The simulated axial strengths were compared with those predicted using AS 5100 and AISC 360. New design equations for the CFDATs should be proposed based on AS 5100.