Introduction: About 300.000 -350.000 Indonesian people suffer from cardiac arrest each year. Basic Life Support (BLS) is the first immediate response needed by cardiac arrest people, especially the out of hospital cardiac arrest (OHCA) patient. BLS that given from public to OHCA could increase the survival rate up to 2 -3x higher. Unfortunately, the Indonesian still did not know what is cardiac arrest, how to recognize it, and how to do BLS. Objective: The objective of this study was to identify the effect of BLS training in the knowledge and skill level of community in Sidodadi Village, Lawang, Indonesia. Method and Material: This experiment used a quasi-experimental design with 102 of the random sampling of people age 20-40 in Sidodadi Village, Lawang, Indonesia. The sample was given pre-test and post-test knowledge questioner before and after joining BLS training. The sample's skill was scored by an assistant doctor using a skill checklist. The data then analysed with a t-paired sample test, Wilcoxon sum rank test, and Pearson correlation. Result and Discussion: The score of women is higher than men both in pre-test and post-test, with the significance of p=0,039 for pre-test and p=0,001. 99% who joined BLS training have a significant increase in knowledge with p=0,001. Conclusion: The increase in knowledge and skill is correlated for an excellent and good level of the score, but not correlated in a bad level. About 99% of people who have joined BLS training have a significant increase in knowledge and skill. These trained people have the willingness to be a bystander for cardiac arrest people near them.Pendahuluan: Sekitar 300.000 -350.000 masyarakat Indonesia mengalami henti jantung setiap tahunnya. Basic Life Support (BLS) adalah pertolongan pertama yang diperlukan oleh korban henti jantung, terutama henti jantung yang terjadi diluar rumah sakit (out of hospital cardiac arrest-OHCA). BLS yang diberikan oleh awam pada OHCA mampu meningkatkan survival rate sebanyak 2 hingga 3x lipat. Sayangnya, masyarakat Indonesia masih banyak yang belum mengetahui apa itu henti jantung, bagaimana cara mengenalinya, dan bagaimana cara melakukan BLS. Tujuan: Tujuan penelitian ini adalah untuk mengetahui pengaruh pelatihan BLS terhadap tingkat pengetahuan dan keterampilan masyarakat dalam memberikan pertolongan pertama henti jantung di Desa Sidodadi, Kecamatan Lawang, Indonesia. Metode dan Bahan: Penelitian ini menggunakan desain quasi eksperimental dengan 102 random sampling dari penduduk berusia 20-40 tahun di Desa Sidodadi, Kecamatan Lawang, Indonesia. Sampel diminta untuk mengisi pretest pengetahuan, mengikuti pelatihan BLS, dan mengisi posttest pengetahuan. Keterampilan sampel dinilai oleh dokter muda menggunakan ceklis keterampilan. Data dianalisis dengan uji t berpasangan, wilcoxon sum rank test, dan uji korelasi pearson. Hasil dan Pembahasan: Nilai pretest dan postest perempuan lebih tinggi daripada pria, dengan nilai signifikansi p=0,039 untuk pretest dan p=0,001. 99% peserta yang mengikuti pelatihan BLS mengalami pen...