Starch foam is a completely biodegradable material that can replace petroleum‐based foams. However, starch foams are sensitive to water and have poor mechanical properties. Khlum fiber that had been alkali‐treated for 1 h (KF‐1h) showed excellent properties as a reinforcement of starch foam. KF‐1h was added to starch at loadings of 0, 1, 3, 5, and 7 wt%. The starch foam composite reinforced with 1 wt% of KF‐1h presented uniformly distributed cells of uniform size, and produced the highest values for flexural stress at maximum load (3.43 MPa), hardness (92.50), and water contact angle (122°) of the studied foams. The modulus of the starch foam composite increased with increments of KF‐1h content but the density and color of the starch foam and the biodegradation process in soil were only slightly affected. This work also demonstrated a practical application of the proposed starch foam composite as a biodegradable food container.