In this study, the ISE-NH4 + sensor based on hybrid membrane of the poly (vinyl chloride)/methyl methacrylate-butyl acrylate 2:8 co-polymer (PVC/MB28) has been successfully developed, where the ratio between PVC: MB28 is 9:1. Meanwhile, the plasticized material used is dioctyl sebacate (DOS) of 66.34 wt. , the amount of lipophilic salt of the potassium tetrakis (4-chlorophenyl) borate (KTpClPB) used is 0.99 wt. , and nonactine as much as 2.97 wt.. The addition of the MB28 co-polymer has successfully improved the performance and mechanical strength of ISE-NH4+ especially at measurements at 40°C. The ISE-NH4 + sensor based on PVC/MB28 has a Nernstian number of 55.4 and 58.7 mV/dec for measurement at 25°C and 40°C with the linear range between 0.1 - 10-5 M. While the ISE-NH4+ sensors based on PVC used as benchmarking have Nernstian numbers of 54.2 and 35.3 mV/dec for measurements at 25 ° C and 40 ° C, where the linear range is 0.1 - 10-5 M and 0.1 - 10-3 M. The addition of MB28 also does not cause the selectivity of the ISE-NH4 + sensor to decrease, where the result of the selectivity between PVC/MB28 is comparable to PVC. © Published under licence by IOP Publishing Ltd.