Teachers can play a crucial role in identifying and responding to children's mental health difficulties. This study explored teachers' mental health literacy (MHL) and their help-giving responses, a topic which is relatively unexplored, particularly at primary school level. Primary teachers (N = 356) responded to a questionnaire that followed the presentation of each of three vignettes: a non-clinical, control, vignette and two clinical vignettes. One of the clinical vignettes described a child with generalised anxiety disorder and another described a child with depression. Mixed-methods questioning was used to assess teachers' ability to recognise internalising disorders and their help-giving responses. Most participants were able to recognise a child experiencing an internalising disorder, with 84% accurately identifying anxiety and 71% accurately identifying depression. Multiple regression analyses showed that being female and having more exposure to mental illness were significantly associated with greater concern for affected children. Greater concern and confidence in one's ability to help students in need were significantly associated with teachers' intention to offer support. More years of teaching experience was associated with less help-giving intentions. MHL training for teachers is recommended so as to improve their ability to identify and respond to children's mental health difficulties in a timely manner.