A composite fiber having elastomer and method for making the same, and a substrate having the composite fiber and method for making the same are provided. The composite fiber includes a first composition and a second composition. The first composition is thermoplastic non-elastomer, and the second composition is thermoplastic elastomer (TPE). The second composition is in an amount of 5 to 70 weight % of the composite fiber. The first composition and the second composition are alternately distributed in a circumference of a cross-section of the composite fiber, and the length of the second composition is less than 50% of the total length of the circumference. The TPE can be dispersed uniformly and increase the adhesion between fibers, and the segmented fiber cross-section thereof further prevents the TPE from becoming too adhesive and affecting the processing during the fabrication of fibers and non-woven fabric substrates. Therefore, the non-woven fabric substrate or artificial leather made from the composite fiber has excellent textile feeling and physical properties.