A flexural strength is one among the predominant factors for the polymer composites under perpendicular loading conditions against the axis of the member. Flexural strength analysis of Jute – Sisal fibred polymer hybrid composite has not been done so for in the literature. Hence in this study, the flexural strength of Ethiopian Jute – Sisal hybrid polyester composite is investigated both analytically and experimentally. It has been analyzed by a Classical theory of Laminates and also simulated using simulation software analytically. Then the laminates have been fabricated by using Hand Lay-up Method and tested under Flexural testing setup of Hydraulic Universal Testing Machine. Composite test specimens have been prepared at various categories as follows. They are based on different sequence of fibre layers : Jute-Sisal-Jute-Sisal(J/S/J/S),Sisal-Jute-Sisal-Jute(S/J/S/J) and Sisal-JuteJute-Sisal(S/J/J/S);fibres arrangement, based on orientation angle of fibres: [00/450/450/00], [00/900/900/00]and [450/00/00/450]; and based on concentration of fibers (weight ratio): [80% Polyester Matrix / 20% Sisal / 0% Jute], [81% Polyester Matrix / 14% Sisal / 5% Jute] and [76% Polyester Matrix / 14% Sisal / 10% Jute]. These sample specimens are then treated with NaOH Solution in the concentration of 6% and 10% and tested for flexural strength according to the standards of Flexural testing for polymers recommended by ASTM D790 – 10. The simulated results from the software ANSYS and the experimental results have been compared. The results are to be found satisfactory with error of 9.4 % on an average. When comparing the results with different angle arrangement, [00/450/450/00] of fiber angled laminates is found to be most effective in flexural strength. And with different concentration of fibers in wt%, 10/14/76 [10% Jute, 14% Sisal and 76% Polyester Matrix] is found to be more satisfactory than the others in the flexural strength. From the Analytical approach, [00/450/450/00] laminate 00 lamina has better strength than 900 lamina. From experimental result in sequence of fiber layers (S/J/S/J) has higher flexural strength than (J/S/J/S) and (S/J/J/S). From experimental result of jute/sisal polyester samples [00/450/450/00] has highest flexural strength which is 111.8 MPa and can resist maximum force of 469.5 N.