Biodegradable hybrid composites were prepared by introducing hydrophilic organic fibres (coconut and date seed powder) into waste high-density polyethylene (WHDPE). Each hybrid polymer composite was prepared with different ratios of fibre loading of coconut shell/sweet date seed powder (5/25%, 10/25%, 15/15%, 20/10% and, 25/5%). 100% WHDPE without any filler was the control sample. The results showed that there was an increase in mechanical properties as the fibres were introduced in the WHDPE with sample 25/5% showing relatively higher superior mechanical properties due to the more crystalline densified structure of the coconut powder compared to the date seed powder. There was also a significant degree of biodegradation (de-polymerization) observed in the hybrid composites compared to WHDPE when they were exposed to the environment averaging at 1.4% per month compared to the WHDPE which averaged at 0.11% biodegradation per month. The results showed that the hybrids can be utilized for industrial and domestic applications and can also undergo biodegradation when disposed, indicating a more environmentally friendly substitute compared to WHDPE.