Several studies have demonstrated that ruminant-fed forages containing bioactive anthelmintics (tannins, alkaloids, and flavonoids) can be used to suppress nematode worms. The objective of this study was to examine any potential direct anthelmintic effects of G.sepium leaves containing Plant Secondary Metabolites (PSM) on the Gastrointestinal Nematode (GIN) in sheep. Twentyfive adult female and male sheep that were naturally infected with nematodes were used in this study. The experimental design utilised a randomised layout with five treatment groups (K1-K5). Each group was composed of five sheep. K1 and K2 received 30% and 50% of their forage feed from G.sepium leaves, respectively, while K3 received 60 g of G.sepium leave powder. Group K4 was a positive control getting the recommended dose of albendazole, and K5 was a negative control (no treatment). Gliricidia sepium leaves and flour was administered every day for 21 days (3 weeks). Evaluation of the anthelmintic effect was conducted using the Fecal Egg Count Reduction Test (FECRT) once a week for 56 days (8 weeks), Packed Cell Volume (PCV) values and faecal culture to detect the dominating growth of nematode larvae types. The results showed that the administration of withered fresh gamal leaves as much as 30% and 50% forages decreased eggs per gram faeces (EPG) in the first until the third week of therapy with faecal egg count reduction of 61-63% and 47-56%, respectively. The effectiveness of G.sepium flour at 60 g/head/day ranged from 26 to 39%. The effectiveness of all group treatments increased after the fourth week of treatment cessation. From the first week of observation until the end of the trial, the EPG of the negative control increased by 30 to > 100%. Most of the sheep showed normal PCV values. The dominant nematode larvae identified were Haemonchus contortus (83.10%),Trichostrongylus sp(15.8%),Oesophagostomum sp (0.83%) and Cooperia sp (0.27%). Haemonchus contortus larvae pose the greatest threat to sheep productivity; consequently, effective control measures are required. These results are highly valuable for farmers, particularly in breeding groups with high helminthiasis prevalence that is challenging to treat with anthelmintics because the majority of ewes are pregnant. The combination of the utilised anthelmintic and Gliricidia sepium leaves will produce the best results in preventing nematodiasis.