The aim of this work is to study the behavior of completely biodegradable starch-based compositescontaining date palm fibers in the range from 20 to 80 wt%. Hybrid composites containing date palmand flax fibers, 25 wt% each, were also examined. The composites were preheated and then hot pressedat 5 MPa and 160◦C for 30 min. SEM investigation showed strong adhesion between fibers and matrix.Density measurements showed very small void fraction (less than 0.142%) for composites containing up to50 wt% fiber content. Increasing fiber weight fraction up to 50 wt% increased the composite static tensileand flexural mechanical properties (stiffness and strength). Composite thermal stability, water uptakeand biodegradation improved with increasing fiber content. The present work shows that starch-basedcomposites with 50 wt% fibers content have the optimum mechanical properties. The hybrid compositeof flax and date palm fibers, 25 wt% each, has good properties and provides a competitive eco-friendlycandidate for various applications.