Cellulose fabrics easily form wrinkles and need ironing treatment to maintain a flat appearance. However, burns and fire accidents caused by ironing clothes have been reported from time to time, as the recommended ironing temperature for cotton fabric is around 180 °C. Herein, an agarose/cellulose composite fiber with easy ironing was successfully prepared via a wet-spinning method by dissolving both agarose and cellulose in a specifically chosen mixed alkali/urea aqueous solution. The composite fiber exhibited superior mechanical properties, with a tensile strength of 164 MPa. Shape memory responses under the influence of water and heat stimulations indicated that the shape fixation ratios were 97−99 and 75−97%, respectively, and the shape recovery ratios were 80−92 and 67−94%, respectively. The composite fiber fabrics have shorter ironing times (2 s) and lower ironing temperatures (92 °C) compared with the regenerated cellulose fiber fabric. Furthermore, the composite fiber showed good dyeability, robust thermal and chemical stability, and a moderate level of biodegradability, capable of complete biodegradation in natural soil within 108 days. This work provided an avenue for fabricating hydrothermal-responsive shape memory fibers that have great potential application in easy ironing garments.