By a labeled graph C * -algebra we mean a C * -algebra associated to a labeled space (E, L, E ) consisting of a labeled graph (E, L) and the smallest normal accommodating set E of vertex subsets. Every graph C * -algebra C * (E) is a labeled graph C * -algebra and it is well known that C * (E) is simple if and only if the graph E is cofinal and satisfies Condition (L). Bates and Pask extend these conditions of graphs E to labeled spaces, and show that if a set-finite and receiver set-finite labeled space (E, L, E ) is cofinal and disagreeable, then its C * -algebra C * (E, L, E ) is simple. In this paper, we show that the converse is also true.2010 Mathematics Subject Classification. 46L05, 46L55.