Poisoning due to deliberate self-harm (DSH) with the seeds of yellow oleander (Thevetia peruviana) results in significant morbidity and mortality each year in South Asia. Yellow oleander seeds contain highly toxic cardiac glycosides including thevetins A and B and neriifolin. A cross-sectional observational study was conducted in Teaching Hospital Batticaloa, SriLanka among all DSH to see the prevalence of yellow oleander poisoning. Out of 121 DSH patients, 33(31.4%), 9 (27.3%) male and 24 (72.7%) female had seeds of yellow oleander poisoning. Among them, 3 (9.1%) patients got 1st-degree heart block while 2 (6.1%) got 2nd- degree heart block and 1(3%) patient got 3rd-degree heart block. Unfortunately, 2 (6.1%) patients have died. Though the numbers of suicide are already quite high, it is estimated that the real figures may be even higher in Sri Lanka. The under‐reporting is due to deaths not being recorded or being misclassified for different reasons such as stigma, legal harassment or insurance benefits. The main reasons for the oleander poisoning were a confrontation with their parents and siblings.