Objective. Social media is increasingly being used to study psychological constructs. This study is the first to use Twitter language to investigate the 24 Values in Action Inventory (VIA) of Character Strengths, which have been shown to predict important life domains such as well-being. Method. We use both a top-down closed-vocabulary (Linguistic Inquiry and Word Count) and a data-driven open-vocabulary (Differential Language Analysis) approach to analyze 3,937,768 tweets from 4,423 participants (64.3% female), who answered a 240-item survey on character strengths. Results. We present the language profiles of (1) a global positivity factor accounting for 36% of the variances in the strengths, and (2) each of the 24 individual strengths, for which we find largely face-valid language associations. Machine learning models trained on language data to predict character strengths reached out-of-sample prediction accuracies comparable to previous work on personality (rmedian = .28, ranging from .13 to .51). Conclusions. The findings suggest that Twitter can be used to characterize and predict character strengths, which could be used to measure the character strengths of large populations unobtrusively and cost-effectively.