Introduction : Acute high-level exposure of cadmium in Danio rerio adult can lead to varying toxic effects. However, several types of researches show exposure CdCl2 caused acute effect toxic to the organ body, so this research aimed to identify lethal concentration 50% (LC50) using a toxicity test. Method : Experimental in vivo post test only method to determine acute LC50 with five dose CdCl2 (20;22,5;25;27,5;30 ppm). Calculating for swimming speed Danio rerio adult was carried out for four groups (control, 0.05 ppm, MATC, and LC50) after exposure. The observation swimming speed in Danio rerio adult during one minute. Observation was carried out using a camera and analysis using Software Tracker. Data analysis used One Way ANOVA and continued Post Hoc LSD with software Statistical Product and Service Solution (SPSS) 16.0 version. Result : Decrease swimming speed with exposure of cadmium dose LC50, MATC, and 0,05 ppm respectively 83%; 61%; and 27% compared with the control group. Conclusion : CdCl2 exposure dose MATC and LC50 to Danio rerio can decrease swimming speed in zebrafish (Danio rerio) adult (p<0,05). Key word : Cadmium (CdCl2), Lethal Concentration 50% (LC50), Swimming Speed, Zebrafish (Danio rerio)