The impact of conflict on the team performance has been discussed widely. Previous investigation generally finds that interpersonal conflict during development IS project can only have a negative impact on project, and it cannot be controlled even through effective processes. However, the investigation merely examines impact to project success measures, but not considers possible beneficial effects on some measures of project development. This work studies the impact of conflict on the quality of the software product as well as project management measures, and on the process as a mediator of formers both. The study result finds that the impact of conflict is negative on both measures indeed and is not fully mediated by effective processes. This implies that researchers and practitioners should turn their attentions earlier in a development project to prevent the detrimental effects of conflict.