This study evaluates the effect of mixing ratio (1, 1.5, 2 and 2.5) and hot air oven pretreatment on the anaerobic co-digestion of water hyacinth and banana peels. Two sets of bio-chemical methane potential (BMP) tests were performed concurrently. In set I, untreated water hyacinth was mixed with banana peels and in set II, water hyacinth was pretreated before co-digestion. Fixed amount of cow dung was added to each reactor as an inoculum. The anaerobic batch test revealed that set II, where pretreated water hyacinth and banana peels was co-digested, demonstrated higher biogas production and better quality of biogas than set I. Mixing ratio 2 and 1.5 were illustrated to be the optimal mixing ratio for set I and II respectively. Both the sets illustrated higher biogas generation than mono-digestion of the substrates. Thus, anaerobic co-digestion of water hyacinth and banana peels portrayed a synergistic action by balancing the overall process. (C) 2018 Elsevier Ltd. All rights reserved.