Broiler chickens are chickens that are raised quickly to produce meat. Broiler chickens have a short growth time because they are genetically modified chickens. Its rapid growth has a negative side: it is easy to get a disease, so the absorption of nutrients does not occur optimally. Farmers in Indonesia usually use antibiotics to overcome this, but antibiotics have a negative impact and are prohibited from being used. An alternative to antibiotics is the probiotic Lacto-B. This study aims to determine the effect of Lacto-B probiotics and the right dose level on broiler chicken performance. The experimental research method used a complete randomized design and ANOVA statistical analysis. Giving Lacto-B probiotics significantly differs (P<0.05) on broiler performance. Probiotic Lacto-B, given at 0.5 ml/liter of drinking water, produces the best broiler chicken performance.