Drawing on linguistic impoliteness, this paper examines offence giving and taking in Twitter Diplomacy in the Middle East, explicating how Twitter affordances shape the context in which offence can be employed strategically in diplomatic communication. The dataset includes all the tweets posted by the Iranian Foreign Minister over a period of 10 years (totaling 659 tweets). The argument expounded in this paper is based on two assumptions. First, impoliteness notions can be effective in analyzing and theorizing diplomatic Tweeting in the times of crisis. Second, diplomatic offence can be employed to manage conflicts and legitimize foreign policies. The results show that diplomatic offence is characteristically explicit, which is vital to index the offender’s disaffiliation from the target’s values. Offence giving is used to present self-image through attacking the adversary’s identity or values, whereas offence taking is utilized to moralize international politics through foregrounding the adversary’s moral idiosyncrasies or legal violations. In effect, diplomatic offence is used to do impression management that aims at gaining moral capital. Twitter affordances allow the affective and moral stances associated with offence giving and taking to be publicized to online and offline audience, encouraging them to align with the producer’s values and political standing.