The integration of artificial intelligence (AI) in education is rapidly expanding, yet many teachers lack formal training in AI literacy and its pedagogical applications. This study explores the perspectives of Swedish K-12 teachers who participated in an online AI training program by Sweden’s largest AI education provider for schools. Using survey data (N = 206), the study examines teachers’ AI attitudes, knowledge acquisition, and classroom applications, guided by UNESCO’s AI Competency Framework. Quantitative analysis, including descriptive statistics, correlation analysis, and ANOVA, reveals that over 85% of teachers lacked formal AI education before training, relying on incidental learning. The training significantly improved AI knowledge, particularly in ethics, with the highest mean score across backgrounds. Digital competence positively influenced AI attitudes and knowledge acquisition, while age and teaching experience correlated negatively. Perceptions of AI integration into education were also shown to vary by subject and school level. Summative content analysis of open-ended responses highlights concerns about student misuse, ethical challenges, and institutional barriers to AI adoption. Despite these concerns, teachers viewed AI as beneficial for lesson planning, resource creation, and personalized learning. Special education and language teachers reported distinct advantages, including multimodal learning support and accessibility improvements for non-native speakers. This study contributes to AI literacy discourse by providing empirical insights into how AI training shapes teaching practices and informs policy recommendations for professional development in AI-integrated education.