This paper studies the extent at which investor sentiment contributes to cryptocurrency return prediction. Investor sentiment is extracted from news articles, Reddit posts and Tweets using BERT-based classifiers fine-tuned on this specific text data. As this data is unlabeled, a weak supervision approach by pseudo-labeling using a zero-shot classifier is used. Contribution of sentiment is then examined using a variety of machine learning models. Each model is trained on data with and without sentiment separately. The conclusion is that sentiment leads to higher prediction accuracy and additional investment profit when the models are analyzed collectively, although this does not hold true for every single model.