The study was conducted to ascertain the effects of interpersonal conflict among Extension staff in Agricultural Development Programme (ADP) in Rivers State, Nigeria. Specifically the study identified the forms of interpersonal conflict among the ADP Extension staff, and ascertained the effects of interpersonal conflict on members of Rivers State ADP Extension staff. A proportionate sampling technique was used to select 149 ADP Extension staff. However, only 135 questionnaires were retrieved from the field. Variables were analyzed and presented using frequency, percentage and mean scores. The result showed that communication conflict and relationship conflict (88.10%) ranked highest forms of conflict in the ADP. The most occurring conflicts were communication conflicts (X̄=3.89), task conflict (X̄=3.77) and power conflict (X̄=3.70). The respondents agreed that interpersonal conflict improves future communication among staff (X̄=3.93), boosts staff morale (X̄=3.93) and improves trust (X̄=3.87). However, they also agreed to these negative effects of interpersonal conflict; apathy (X̄=3.93), distraction (X̄=3.76) and low morale (X̄=3.75). The study concluded that interpersonal conflict improves future communication, boosts staff morale and improves trust. On the contrary; interpersonal conflict leads to apathy, distraction and low morale. It was recommended that government and employers should make Conflict management and resolution as part of compulsory Continuous Professional Development (CPD) for staff of the ADP. This will effectively utilize positive effects of interpersonal conflict while minimizing the negative effects for a more productive organization.