The cacao pod husk (CPH) produced as an agricultural waste by-product during the cacao bean processing. To reach the sustainable development goals on waste recycling, CPH was applied to extract CPH pectin for developing the potential for diverse application in aquaculture, minimizing CPH impact to the environment and bringing benefits to the agriculture and aquaculture industries. There are five treatments in this study including (1) basal diet (BD), (2) CPH pectin (5 g/kg diet, CPH), (3) Lactobacillus plantarum (1010 cfu/kg diet, LP10), and two synbiotic combinations of (4) CPH pectin at 5 g/kg diet + LP at 107 cfu/kg diet (CPH+LP7) (5) CPH pectin at 5 g/kg diet + LP at 1010 cfu/kg diet (CPH+LP10). After the 56-day feeding trial, significantly elevated percent weight gain, percent length gains and feeding efficiency in Litopenaeus vannamei were only observed in CPH+LP7, and the remainder of the treatments remained consistently similar to the BD. The total haemocyte count, granular cells, phenoloxidase activity, and respiratory bursts of L. vannamei fed with CPH+LP7 and CPH+LP10 are significantly increases at 7–28 days, accompanied by significant promotion of phagocytic activity and clearance efficiency in response to Vibrio alginolyticus challenge during 56 days of feeding trial. Furthermore, at the end of the 56 days of feeding trial, shrimp receiving CPH pectin and/or LP treatments showed a significantly higher survival ratio against V. alginolyticus infection and hypothermal stress. It was therefore concluded that the synbiotic combination of CPH pectin and LP exhibited complementary and synergistic effects on growth performance and immunocompetence in L. vannamei within 56 days of feeding trial.