Noisy user-generated text poses problems for natural language processing. In this paper, we show that this statement also holds true for the Irish language. Irish is regarded as a low-resourced language, with limited annotated corpora available to NLP researchers and linguists to fully analyse the linguistic patterns in language use in social media. We contribute to recent advances in this area of research by reporting on the development of part-of speech annotation scheme and annotated corpus for Irish language tweets. We also report on state-of-the-art tagging results of training and testing three existing POStaggers on our new dataset.