Given the increasing use of online platforms, the current research comprised two studies examining links between personality and emoticon use: Study 1 explored the psychological factors associated with emoticon usage on different online platforms (N = 92), and Study 2 assessed the accuracy of a group of observers' personality judgements of Facebook users (N = 54). Participants in Study 1 comprised previously unacquainted dyads who each completed measures on their Big-5 personality, self-esteem, social anxiety, self-presentation, and self-reported usage of emoticons on email, text messages and Facebook. Participants provided Facebook data and interacted online with each other for 10-min. Trait analysis revealed that agreeableness was positively related to self-reported emoticon usage on Facebook, but not in texts or emails. In Study 2, observers viewed the Facebook stimuli and made personality assessments of the dyad members. Judgement accuracy was determined by correlating these assessments with targets' own self-reported personality. Analyses revealed the highest level of accuracy for extraversion and openness. Finally, positive correlations were found between objective usage of “happy” emoticons and observers' assessments of targets’ agreeableness, conscientiousness and openness. Taken together, findings indicate the importance of specific online behaviours in self-presentation, and their impact on judgement accuracy.