According to the invention, there is provided a novel soybean variety designated XB15A08. This invention thus relates to the seeds of soybean variety XB15A08, to the plants of soybean XB15A08 to plant parts of soybean variety XB15A08 and to methods for producing a soybean plant produced by crossing plants of the soybean variety XB15A08 with another soybean plant, using XB15A08 as either the male or the female parent.